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Takes first steps towards sprite display on the TMS.

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This commit is contained in:
Thomas Harte 2017-12-02 22:13:43 -05:00
parent e4534775b0
commit 38b11893e8
2 changed files with 145 additions and 13 deletions
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148
Components/9918/9918.cpp
View File

@ -135,10 +135,48 @@ void TMS9918::run_for(const HalfCycles cycles) {
case LineMode::Character:
while(access_pointer_ < access_slot) {
if(access_pointer_ < 26) {
access_pointer_ = std::min(26, access_slot);
// Four access windows: no collection.
access_pointer_ = std::min(4, access_slot);
// Then ten access windows are filled with collection of sprite 3 and 4 details.
if(access_pointer_ >= 4 && access_pointer_ < 14) {
// TODO: this repeats the code below.
while(access_pointer_ < access_slot) {
const int target = 2 + (access_pointer_ - 4) / 6;
const int sprite = active_sprites_[target] & 31;
const int subcycle = access_pointer_ % 6;
switch(subcycle) {
case 2: sprites_[target].y = ram_[sprite_attribute_table_address_ + (sprite << 2)]; break;
case 3: sprites_[target].x = ram_[sprite_attribute_table_address_ + (sprite << 2) + 1]; break;
case 4: sprites_[target].pattern_number = ram_[sprite_attribute_table_address_ + (sprite << 2) + 2]; break;
case 5: sprites_[target].colour = ram_[sprite_attribute_table_address_ + (sprite << 2) + 3]; break;
case 0:
case 1: {
const int sprite_offset = sprites_[target].pattern_number & ~(sprites_16x16_ ? 3 : 0);
const int sprite_row = (row_ - sprites_[target].y) & 15;
const int sprite_address =
sprite_generator_table_address_ + (sprite_offset << 3) + sprite_row + ((subcycle - 4) << 4);
sprites_[target].pattern[subcycle - 4] = ram_[sprite_address];
} break;
}
access_pointer_++;
}
}
if(access_pointer_ >= 26) {
// Four more access windows: no collection.
access_pointer_ = std::min(18, access_slot);
// Then eight access windows fetch the y position for the first eight sprites.
if(access_pointer_ >= 18 && access_pointer_ < 26) {
while(access_pointer_ < 26) {
const int sprite = access_pointer_ - 18;
sprite_locations_[sprite] = ram_[sprite_attribute_table_address_ + (sprite << 2)];
access_pointer_++;
}
}
// The next 128 access slots are video and sprite collection interleaved.
if(access_pointer_ >= 26 && access_pointer_ < 154) {
int end = std::min(154, access_slot);
int row_base = pattern_name_address_;
@ -150,31 +188,105 @@ void TMS9918::run_for(const HalfCycles cycles) {
}
row_base += (row_ << 2)&~31;
// Sprites 0–7: 18–25; then:
// 31, 35, 39 ... 47, 51, 55 ... 63, 67, 71 ... 79, 83, 87 ...
// 95, 99, 103 ... 111, 115, 119 ... 127, 131, 135 ... 143, 147, 151
//
// Relative to 31:
// 0, 4, 8, X, ...
// TODO: optimise this mess.
while(access_pointer_ < end) {
int character_column = ((access_pointer_ - 26) >> 2);
switch(access_pointer_&3) {
case 0:
case 2:
pattern_name_ = ram_[row_base + character_column];
break;
case 1: break; // TODO: sprites / CPU access.
case 2:
case 3: {
const int slot = (access_pointer_ - 31) >> 2;
if((slot&3) == 3)
break;
const int sprite = slot - (slot >> 2) + 8;
sprite_locations_[sprite] = ram_[sprite_attribute_table_address_ + (sprite << 2)];
} break; // TODO: sprites / CPU access.
case 0:
if(screen_mode_ != 1) {
colour_buffer_[character_column] = ram_[colour_base + (pattern_name_ >> 3)];
} else {
colour_buffer_[character_column] = ram_[colour_base + (pattern_name_ << 3) + (row_ & 7)];
}
break;
case 3:
case 1:
pattern_buffer_[character_column] = ram_[pattern_base + (pattern_name_ << 3) + (row_ & 7)];
break;
}
access_pointer_++;
}
if(access_pointer_ == 154) {
// Pick some sprites to display.
active_sprites_[0] = active_sprites_[1] = active_sprites_[2] = active_sprites_[3] = 0xff;
int slot = 0;
int last_visible = 0;
int sprite_height = 8;
if(sprites_16x16_) sprite_height <<= 1;
if(sprites_magnified_) sprite_height <<= 1;
for(int c = 0; c < 32; ++c) {
// A sprite Y of 208 means "don't scan the list any further".
if(sprite_locations_[c] == 208) break;
// Skip sprite if invisible anyway.
int ranged_location = ((static_cast<int>(sprite_locations_[c]) + sprite_height) & 255) - sprite_height;
if(ranged_location > row_ || ranged_location + sprite_height < row_) continue;
last_visible = c;
if(slot < 4) {
active_sprites_[slot] = c;
slot++;
} else {
// Set the fifth sprite bit and store the sprite if this is the first encountered.
if(!(status_ & 0x40)) {
status_ |= 0x40;
status_ = (status_ & ~31) | c;
}
break;
}
}
if(!(status_ & 0x40)) {
status_ = (status_ & ~31) | last_visible;
}
}
}
if(access_pointer_ >= 154) {
access_pointer_ = access_slot;
// Two access windows: no collection.
access_pointer_ = std::min(156, access_slot);
// Fourteen access windows: collect initial sprite information.
if(access_pointer_ >= 156 && access_pointer_ < 170) {
while(access_pointer_ < access_slot) {
const int target = (access_pointer_ - 156) / 6;
const int sprite = active_sprites_[target] & 31;
const int subcycle = access_pointer_ % 6;
switch(subcycle) {
case 0: sprites_[target].y = ram_[sprite_attribute_table_address_ + (sprite << 2)]; break;
case 1: sprites_[target].x = ram_[sprite_attribute_table_address_ + (sprite << 2) + 1]; break;
case 2: sprites_[target].pattern_number = ram_[sprite_attribute_table_address_ + (sprite << 2) + 2]; break;
case 3: sprites_[target].colour = ram_[sprite_attribute_table_address_ + (sprite << 2) + 3]; break;
case 4:
case 5: {
const int sprite_offset = sprites_[target].pattern_number & ~(sprites_16x16_ ? 3 : 0);
const int sprite_row = (row_ - sprites_[target].y) & 15;
const int sprite_address =
sprite_generator_table_address_ + (sprite_offset << 3) + sprite_row + ((subcycle - 4) << 4);
sprites_[target].pattern[subcycle - 4] = ram_[sprite_address];
} break;
}
access_pointer_++;
}
}
// There's another unused access window here.
}
break;
}
@ -213,7 +325,7 @@ void TMS9918::run_for(const HalfCycles cycles) {
// Grab a pointer for drawing pixels to, if the moment has arrived.
if(pixels_end == first_pixel_column_) {
pixel_target_ = reinterpret_cast<uint32_t *>(crt_->allocate_write_area(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_)));
pixel_base_ = pixel_target_ = reinterpret_cast<uint32_t *>(crt_->allocate_write_area(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_)));
}
}
}
@ -254,6 +366,18 @@ void TMS9918::run_for(const HalfCycles cycles) {
}
if(output_column_ == first_right_border_column_) {
// Just chuck the sprites on. Quick hack!
for(size_t c = 0; c < 4; ++c) {
if(active_sprites_[c^3] == 255) continue;
for(int p = 0; p < (sprites_16x16_ ? 16 : 8); ++p) {
int x = sprites_[c^3].x + p;
if(sprites_[c^3].colour & 0x80) x -= 32;
if(x >= 0 && x < 256) {
if(((sprites_[c^3].pattern[p >> 3] << (p&7)) & 0x80)) pixel_base_[x] = palette[sprites_[c^3].colour & 15];
}
}
}
crt_->output_data(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_), 1);
pixel_target_ = nullptr;
}
@ -407,9 +531,9 @@ uint8_t TMS9918::get_register(int address) {
return result;
}
// Reads from address 1 get the status register;
// Reads from address 1 get the status register.
uint8_t result = status_;
status_ &= ~(0x80 | 0x20);
status_ &= ~(0x80 | 0x40 | 0x20);
return result;
}

10
Components/9918/9918.hpp
View File

@ -78,7 +78,7 @@ class TMS9918 {
HalfCycles half_cycles_into_frame_;
int column_ = 0, row_ = 0, output_column_ = 0;
int cycles_error_ = 0;
uint32_t *pixel_target_ = nullptr;
uint32_t *pixel_target_ = nullptr, *pixel_base_ = nullptr;
void output_border(int cycles);
@ -95,8 +95,16 @@ class TMS9918 {
uint8_t pattern_buffer_[40];
uint8_t colour_buffer_[40];
uint8_t sprite_locations_[32];
uint8_t active_sprites_[4];
int access_pointer_ = 0;
uint8_t pattern_name_ = 0;
struct Sprite {
uint8_t x, y;
uint8_t colour, pattern_number;
uint8_t pattern[2];
} sprites_[4];
};
};