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327 lines
16 KiB
HTML
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<title>Visualizations - 6502bench SourceGen</title>
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<h1>SourceGen: Visualizations</h1>
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<p><a href="index.html">Back to index</a></p>
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<h2 id="overview">Overview</h2>
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<p>Programs are generally a combination of code and data. Sometimes
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the data is graphical in nature, e.g. a bitmap used as a font or
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game sprite. Being able to see the data in graphic form can make it
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easier to determine the purpose of associated code.</p>
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<p>While modern systems use GIF, JPEG, and PNG to hold 2D bitmaps,
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graphical elements embedded in 6502 applications are almost always
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in a platform-specific form. For this reason, the task of generating
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images from data is performed by
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<a href="advanced.html#extension-scripts">extension scripts</a>. Some
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scripts for common formats are included in the SourceGen runtime directory.
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If these don't do what you need, you can write your own scripts and
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include them in your project.</p>
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<p>The project file doesn't store the converted graphics. Instead, the
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project file holds a string that identifies the converter, and a list of
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parameters that are passed to the converter. Images are generated when
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the project is first opened, and updated when certain things change in
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the project.</p>
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<p>Visualizations are not included in generated assembly output. They
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may be included in HTML exports.</p>
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<p>Because visualizations are associated with a specific file offset,
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they will become "hidden" if the offset isn't at the start of a line,
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e.g. it's in the middle of a multi-byte instruction or data item. The
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editors will try to prevent you from doing this.</p>
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<p>Bitmaps will always be scaled up as much as possible to make them
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easy to see. This means that small shapes and large shapes may appears
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to be the same size when displayed as thumbnails in the code list.</p>
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<p>The role of a visualization generator is to take a collection of input
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parameters and generate graphical data. It's most useful for graphical
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sources like bitmaps, but it's not limited to that. You could, for example,
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write a script that generates random flowers, and use it to make your
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source listings more cheerful.</p>
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<h2 id="vis-and-sets">Visualizations and Visualization Sets</h2>
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<p>Visualizations are essentially decorative: they do not affect the
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assembled output, and do not change how code is analyzed. They are
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contained in sets that are placed at arbitrary offsets. Each set can
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contain multiple items. For example, if a file has data for
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10 bitmaps, you can place a visualization near each, or create a single
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visualization set with all 10 items and put it at the start of the file.
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You can display a visualization near the data or near the instructions
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that perform the drawing. Or both.</p>
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<p>To create a visualization set, select a code or data line, and use
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<samp>Actions > Create/Edit Visualization Set</samp>. To edit
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a visualization set, select it and use the same menu item, or just
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double-click on it. This opens the Visualization Set Editor window.</p>
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<p>The visualization set editor shows a list of visualizations associated
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with the selected file offset. You can create a new visualization, edit
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or remove an existing entry, or rearrange them.
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If you select <samp>New Bitmap</samp> or edit an existing bitmap entry, the
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Bitmap Visualization Editor window will open.
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Similarly, if you select <samp>New Bitmap Animation</samp> or edit an
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existing bitmap animation, the Bitmap Animation Editor will open.</p>
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<h4>Visualization Editor</h4>
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<p>The combo box at the top of the screen lists every visualization
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generator defined by an active extension script. Select the one that is
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appropriate for the data you're trying to visualize. Every visualizer may
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have different parameters, so as you select different entries the set of
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input parameters below the preview window may change.</p>
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<p>There are two categories of visualization generator: bitmap, and
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wireframe. Bitmaps are simple 2D images, but wireframes are 2D or 3D
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meshes that can be viewed from different angles. When you select a
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wireframe generator, additional view controls will be added at the bottom.
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(See below.)</p>
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<p>The "tag" is a unique string that will be shown in the display list.
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This is not a label, and may contain any characters you want (but leading
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and trailing whitespace will be trimmed). The only requirement is that
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it be unique across all visualizations (bitmaps, animations, etc).</p>
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<p>The preview window shows the visualizer output. The generated image is
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expanded to fill the window, so small bitmaps will be shown with very
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large pixels.
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If you resize the editor window, the preview window will expand, which
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can make it easier to see detail on larger images.
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If the generator fails, the preview window will show a red 'X', and an
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error message will appear below it.</p>
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<p>Parameters may be numeric or boolean. The latter use a simple checkbox,
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the former a text entry field that accepts decimal and hexadecimal values.
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The range of allowable values is shown to the right of the entry field.
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If you enter an invalid value, the parameter description will turn red.</p>
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<p>The <samp>Export</samp> button at the top right can be used to save a
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copy of the bitmap or wireframe rendering with the current parameters.</p>
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<h5>Wireframe View Controls</h5>
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<p>The wireframe generator may offer the choice of perspective vs.
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orthographic projection, and whether or not to enable backface
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culling. These are declared in the visualization generator script,
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but implemented in the viewer. If the generator doesn't
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declare them, the default is to render with a perspective projection
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and without culling.</p>
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<p>The viewer allows you to rotate the image about the X, Y, and Z
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axes. The viewer provides a left-handed coordinate system,
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with +X toward the right, +Y toward the top of the screen, and +Z
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going into the screen. The object will be placed a short distance
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down the Z axis and scaled to fit the window.
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Positive rotations cause a counter-clockwise rotation when the axis
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about which rotations are performed points toward the viewer. The
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rotations are performed with a matrix using Euler angles, and are
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subject to gimbal lock (e.g. if you set Y to 90 degrees, X and Z rotate
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about the same axis).</p>
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<p>If you check the <samp>Animated</samp> box, you can add a simple spin.
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Choose the number of degrees to rotate per frame, how many frames to
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generate before resetting, and the delay between each frame. Clicking
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the <samp>Auto</samp> button will automatically select the number of
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frames needed to display the animation in an unbroken loop (useful
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for animated GIFs). Click the <samp>Test Animation</samp> button to
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see it in action.</p>
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<h4>Bitmap Animation Editor</h4>
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<p>Bitmap animations allow you to create a simple animation from a
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collection of other visualizations. This can be useful when a program
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stores animated graphics as a series of frames.</p>
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<p>The "tag" is a unique string that will be shown in the display list.
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The same rules apply as for bitmap visualizations.</p>
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<p>The list at the top left holds all visualizations. Select items on
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the left and use the <samp>Add</samp> button to add them to the list on
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the right, which has the set that is included in the animation. You
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can reorder the list with the up/down buttons. Adding the same frame
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multiple times is allowed.</p>
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<p>The <samp>frame delay</samp> field lets you specify how long each
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frame is shown on screen, in milliseconds. Some animation formats may
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use a different time resolution; for example, animated GIFs use units
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of 1/100th of a second. The closest value will be used. Note also
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that some viewers (notably web browsers) will cap the update rate.</p>
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<p>When you have one or more frames in the animation list, you can preview
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the result in the window at the bottom. The actual appearance may be
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slightly different, especially if the frames are different sizes. For
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example, the preview window scales individual frames, but animated GIFs
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will be scaled to the size of the largest frame.</p>
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<h2 id="runtime">Scripts Included with SourceGen</h2>
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<p>A number of visualization generation scripts are included with
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SourceGen, in the platform-specific runtime data directories.</p>
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<p>Most generators will take the file offset, bitmap width, and bitmap
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height as parameters. Offsets are handled as they are elsewhere, i.e.
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always in hexadecimal, with a leading '+'.
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Some less-common parameters include:</p>
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<ul>
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<li><b>Column stride</b> - number of bytes used to hold a column.
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This is uncommon, but could be used if (say) a pair of bitmaps
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was stored with interleaved bytes. If you set this to zero the
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visualizer will default to no interleave (col_stride = 1).</li>
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<li><b>Row stride</b> - number of bytes between the start of each
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row. This is used when a row has padding on the end, e.g. a
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bitmap that's 7 bytes wide might be padded to 8 for easy indexing,
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or when bitmap data is interleaved. If you set this to zero the
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visualizer will default to no padding
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(row_stride = width * column_stride).</li>
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<li><b>Cell stride</b> - for multi-bitmap data like a font or sprite
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sheet, this determines the number of bytes between the start of
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one item and the next. If set to zero a "dense" arrangement is
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assumed (cell_stride = row_stride * item_height).</li>
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</ul>
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<p>Remember that this is a disassembler, not an image converter. The
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results do not need to be perfectly accurate to be useful when disassembling
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code.</p>
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<h3>Apple II : Apple/VisHiRes and Apple/VisShapeTable</h3>
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<p>There is no standard format for small hi-res bitmaps, but certain
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arrangements are common. The VisHiRes script defines four generators:</p>
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<ul>
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<li><b>Hi-Res Bitmap</b> - converts an MxN row-major bitmap.</li>
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<li><b>Hi-Res Sprite Sheet</b> - converts a series of bitmaps and
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renders them in a grid. Useful for games that use cell
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animation. The generated bitmap has a 1-pixel transparent gap
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between elements.</li>
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<li><b>Hi-Res Bitmap Font</b> - a simplified version of the
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Sprite Sheet, intended for the common 7x8 monochrome fonts.
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Most fonts have 96 or 128 glyphs, though some drop the last
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character.
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(This also works for Apple /// fonts, but currently ignores
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the high bit in each byte.)</li>
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<li><b>Hi-Res Screen Image</b> - used for 8KiB screen images. The
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data is linearized and converted to a 280x192 bitmap. Because
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images are relatively large, the generator does not require them
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to be contiguous in the file, i.e. two halves of the image can be
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in different parts of the file so long as they end up contiguous
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in memory.</li>
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</ul>
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<p>Widths are specified in bytes, not pixels. Each byte represents 7
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pixels (with some hand-waving).</p>
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<p>In addition to offset, dimensions, and stride values, the bitmap
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converter has a checkbox for monochrome or color, and two checkboxes
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that affect the color. The first causes the first byte to be treated
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as being in an odd column rather than an even one, which affects
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green vs. purple and orange vs. blue. The second flips the high bits
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on every byte, switching green vs. orange and purple vs. blue.
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Neither has any effect on black & white bitmaps.</p>
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<p>The converter generates one output pixel for every source pixel, so
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half-pixel shifts are not represented.</p>
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<p>The VisShapeTable script renders Applesoft shape tables, which can
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have multiple vector shapes. The only parameter other than the offset
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is the shape number.</p>
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<h3>Atari 2600 : Atari/Vis2600</h3>
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<p>The Atari 2600 graphics system has registers that determine the
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appearance of a sprite or playfield on a single row. The register
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values are typically changed as the screen is drawn to get different
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data on successive rows. The visualization generator doesn't attempt
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to emulate this behavior, but works well for data stored in a
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straightforward fashion.</p>
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<ul>
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<li><b>Sprite</b> - basic 1xN sprite, converted to an image 8 pixels
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wide. Square pixels are assumed.</li>
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<li><b>Playfield</b> - assumes PF0,PF1,PF2 are stored in that order,
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multiple entries following each other. Specify the number of
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3-byte entries as the height.
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Since most playfields aren't the full height of the screen,
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it will tend to look squashed. Use the "row thickness" feature
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to repeat each row N times to adjust the proportions.
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The "Reflected" checkbox determines whether the right-side image is
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repeated as-is or flipped.</li>
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</ul>
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<h3>Atari Arcade : Atari/VisAVG and Atari/VisDVG</h3>
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<p>Different versions of Atari's Analog Vector Graphics and
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Digital Vector Graphics were used in several games, notably Asteroids,
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Battlezone, Tempest, and Star Wars. The commands
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drove a vector display monitor. SourceGen visualizes them as 2D
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wireframes, which isn't a perfect fit since they can describe points as
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well as lines, but works fine for annotating a disassembly.</p>
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<p>The visualizer takes two arguments: the offset of the start of
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the commands to visualize, and the base address of vector RAM. The latter
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is needed to convert vector JMP/JSR commands into offsets.</p>
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<h3>Commodore 64 : Commodore/VisC64</h3>
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<p>The Commodore 64 has a 64-byte sprite format defined by the hardware.
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It comes in two basic varieties:</p>
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<ul>
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<li><b>High-resolution sprite</b> - 24x21 monochrome. Pixels are either
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colored or transparent.</li>
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<li><b>Multi-color sprite</b> - 12x21 3-color. The width of each pixel
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is doubled to make it 24x21.
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</ul>
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<p>Sprites can be doubled in width and/or height.</p>
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<p>Colors come from a hardware-defined palette of 16:</p>
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<ol start="0" style="columns:2; -webkit-columns:2; -moz-columns:2;">
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<li><span style="color:#ffffff;background-color:#000000"> black </span></li>
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<li><span style="color:#000000;background-color:#ffffff"> white </span></li>
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<li><span style="color:#ffffff;background-color:#67372b"> red </span></li>
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<li><span style="color:#ffffff;background-color:#70a4b2"> cyan </span></li>
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<li><span style="color:#ffffff;background-color:#6f3d86"> purple </span></li>
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<li><span style="color:#ffffff;background-color:#588d43"> green </span></li>
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<li><span style="color:#ffffff;background-color:#352879"> blue </span></li>
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<li><span style="color:#000000;background-color:#b8c76f"> yellow </span></li>
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<li><span style="color:#ffffff;background-color:#6f4f25"> orange </span></li>
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<li><span style="color:#ffffff;background-color:#433900"> brown </span></li>
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<li><span style="color:#ffffff;background-color:#9a6759"> light red </span></li>
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<li><span style="color:#ffffff;background-color:#444444"> dark grey </span></li>
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<li><span style="color:#ffffff;background-color:#6c6c6c"> grey </span></li>
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<li><span style="color:#000000;background-color:#9ad284"> light green </span></li>
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<li><span style="color:#ffffff;background-color:#6c5eb5"> light blue </span></li>
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<li><span style="color:#ffffff;background-color:#959595"> light grey </span></li>
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</ol>
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<p>Bear in mind that the editor scales images to their maximum size, so
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a sprite that is doubled in both width and height will look exactly like
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a sprite that is not doubled at all.</p>
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<p>If multiple sprites are defined consecutively, at 64-byte intervals,
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they can be combined into a sprite sheet. A single set of parameters
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for color and scaling is applied to all sprites.</p>
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<p>The visualizer also handles high-resolution and multi-color fonts,
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which are displayed in a grid.</p>
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<h3>Nintendo Entertainment System : Nintendo/VisNES</h3>
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<p>NES PPU pattern tables hold 8x8 tiles with 2 bits of color per pixel.
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Converting the full collection to a reference bitmap is straightforward.
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A few color palette options are offered.</p>
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<p>Sprites and backgrounds are formed from collections of tiles. In
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some cases this is straightfoward, in others it's not. A visualization
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generator that renders a "tile grid" is available for simpler cases.</p>
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