added cube3d-gfx example

examples/c64graphics.p8

@@ -13,6 +13,10 @@ graphics {
         ; enable bitmap screen, erase it and set colors to black/white.
         c64.SCROLY |= %00100000
         c64.VMCSB = (c64.VMCSB & %11110000) | %00001000   ; $2000-$3fff
+        clear_screen()
+    }
+
+    sub clear_screen() {
         memset(bitmap_address, 320*200/8, 0)
         c64scr.clear_screen($10, 0)         ; pixel color $1 (white) backround $0 (black)
     }

examples/cube3d-gfx.p8

@@ -0,0 +1,95 @@
+%import c64lib
+%import c64utils
+%import c64graphics
+
+
+main {
+
+    const uword width = 255
+    const uword height = 200
+
+    ; vertices
+    word[] xcoor = [ -100, -100, -100, -100,  100,  100,  100, 100 ]
+    word[] ycoor = [ -100, -100,  100,  100, -100, -100,  100, 100 ]
+    word[] zcoor = [ -100,  100, -100,  100, -100,  100, -100, 100 ]
+
+    ; storage for rotated coordinates
+    word[len(xcoor)] rotatedx
+    word[len(ycoor)] rotatedy
+    word[len(zcoor)] rotatedz
+
+    ; edges
+    ubyte[] edgesFrom = [ 0, 2, 6, 4, 1, 3, 7, 5, 0, 2, 6, 4]
+    ubyte[] edgesTo = [ 2, 6, 4, 0, 3, 7, 5, 1, 1, 3, 7, 5]
+
+
+    sub start()  {
+        uword anglex
+        uword angley
+        uword anglez
+
+        graphics.enable_bitmap_mode()
+
+
+        repeat {
+            rotate_vertices(msb(anglex), msb(angley), msb(anglez))
+            graphics.clear_screen()
+            draw_lines()
+            anglex-=500
+            angley+=217
+            anglez+=452
+
+            while c64.RASTER!=255 {
+            }
+            while c64.RASTER!=254 {
+            }
+        }
+    }
+
+    sub rotate_vertices(ubyte ax, ubyte ay, ubyte az) {
+        ; rotate around origin (0,0,0)
+
+        ; set up the 3d rotation matrix values
+        word wcosa = cos8(ax)
+        word wsina = sin8(ax)
+        word wcosb = cos8(ay)
+        word wsinb = sin8(ay)
+        word wcosc = cos8(az)
+        word wsinc = sin8(az)
+
+        word wcosa_sinb = wcosa*wsinb / 128
+        word wsina_sinb = wsina*wsinb / 128
+
+        word Axx = wcosa*wcosb / 128
+        word Axy = (wcosa_sinb*wsinc - wsina*wcosc) / 128
+        word Axz = (wcosa_sinb*wcosc + wsina*wsinc) / 128
+        word Ayx = wsina*wcosb / 128
+        word Ayy = (wsina_sinb*wsinc + wcosa*wcosc) / 128
+        word Ayz = (wsina_sinb*wcosc - wcosa*wsinc) / 128
+        word Azx = -wsinb
+        word Azy = wcosb*wsinc / 128
+        word Azz = wcosb*wcosc / 128
+
+        ubyte i
+        for i in 0 to len(xcoor)-1 {
+            ; don't normalize by dividing by 128, instead keep some precision for perspective calc later
+            rotatedx[i] = (Axx*xcoor[i] + Axy*ycoor[i] + Axz*zcoor[i])
+            rotatedy[i] = (Ayx*xcoor[i] + Ayy*ycoor[i] + Ayz*zcoor[i])
+            rotatedz[i] = (Azx*xcoor[i] + Azy*ycoor[i] + Azz*zcoor[i])
+        }
+    }
+
+    sub draw_lines() {
+        ubyte i
+        for i in len(edgesFrom) -1 downto 0 {
+            ubyte vFrom = edgesFrom[i]
+            ubyte vTo = edgesTo[i]
+            word persp1 = 256 + rotatedz[vFrom]/256
+            word persp2 = 256 + rotatedz[vTo]/256
+            graphics.line(rotatedx[vFrom] / persp1 + 160.w as uword,
+                          rotatedy[vFrom] / persp1 + 100 as ubyte,
+                          rotatedx[vTo] / persp2 + 160.w as uword,
+                          rotatedy[vTo] / persp2 + 100 as ubyte)
+        }
+    }
+}

examples/cube3d-sprites.p8

@@ -65,9 +65,9 @@ main {
     const uword height = 200
 
     ; vertices
-    byte[] xcoor = [ -100, -100, -100, -100,  100,  100,  100, 100 ]
-    byte[] ycoor = [ -100, -100,  100,  100, -100, -100,  100, 100 ]
-    byte[] zcoor = [ -100,  100, -100,  100, -100,  100, -100, 100 ]
+    word[] xcoor = [ -100, -100, -100, -100,  100,  100,  100, 100 ]
+    word[] ycoor = [ -100, -100,  100,  100, -100, -100,  100, 100 ]
+    word[] zcoor = [ -100,  100, -100,  100, -100,  100, -100, 100 ]
 
     ; storage for rotated coordinates
     word[len(xcoor)] rotatedx

examples/cube3d.p8

@@ -7,9 +7,9 @@ main {
     const uword height = 25
 
     ; vertices
-    byte[] xcoor = [ -40, -40, -40, -40,  40,  40,  40, 40 ]
-    byte[] ycoor = [ -40, -40,  40,  40, -40, -40,  40, 40 ]
-    byte[] zcoor = [ -40,  40, -40,  40, -40,  40, -40, 40 ]
+    word[] xcoor = [ -40, -40, -40, -40,  40,  40,  40, 40 ]
+    word[] ycoor = [ -40, -40,  40,  40, -40, -40,  40, 40 ]
+    word[] zcoor = [ -40,  40, -40,  40, -40,  40, -40, 40 ]
 
     ; storage for rotated coordinates
     word[len(xcoor)] rotatedx