Emulator: Add naive background tile rendering to PPU

src/main.cpp

@@ -9,6 +9,7 @@
 
 #include "inferno.h"
 #include "inferno/entrypoint.h"
+#include "ppu.h"
 #include "ruc/argparser.h"
 #include "ruc/format/print.h"
 #include "ruc/timer.h"
@@ -47,6 +48,8 @@ public:
 
 	void render() override
 	{
+		auto* ppu = static_cast<PPU*>(Emu::the().processingUnit("PPU").get());
+		ppu->render();
 	}
 };
 

src/ppu.cpp

@@ -6,14 +6,31 @@
  */
 
 #include <cstdint> // uint32_t
+#include <memory>  // std::make_shared
+
+#include "glm/ext/vector_float3.hpp" // glm::vec3
+#include "glm/ext/vector_float4.hpp" // glm::vec4
+#include "inferno/application.h"
+#include "inferno/component/spritecomponent.h"
+#include "inferno/component/transformcomponent.h"
+#include "inferno/scene/scene.h"
+#include "ruc/format/print.h"
 
 #include "emu.h"
 #include "ppu.h"
-#include "ruc/format/print.h"
 
 PPU ::PPU(uint32_t frequency)
 	: ProcessingUnit(frequency)
 {
+	auto& scene = Inferno::Application::the().scene();
+	m_entity = scene.createEntity("Screen");
+
+	// Flip the screen to accommodate OpenGL's coordinate system
+	auto& transform = scene.getComponent<Inferno::TransformComponent>(m_entity);
+	transform.scale.y = -1.0f;
+
+	auto texture = std::make_shared<Inferno::Texture>(m_screen.data(), SCREEN_WIDTH, SCREEN_HEIGHT, FORMAT_SIZE);
+	scene.addComponent<Inferno::SpriteComponent>(m_entity, glm::vec4 { 1.0f }, texture);
 }
 
 PPU ::~PPU()
@@ -36,3 +53,91 @@ void PPU::update()
 	}
 	Emu::the().writeMemory(0xff44, ly_register);
 }
+
+void PPU::render()
+{
+	LCDC lcd_control = static_cast<LCDC>(Emu::the().readMemory(0xff40));
+
+	if (!(lcd_control & LCDC::BGandWindowEnable)) {
+		// When Bit 0 is cleared, both background and window become blank (white)
+		m_screen.fill(255);
+	}
+	else {
+		// Tile map
+		uint32_t tile_map_size = 32 * 32; // 1 KiB
+		uint32_t bg_tile_map_address = (lcd_control & LCDC::BGTileMapArea) ? 0x9c00 : 0x9800;
+		// uint32_t window_tile_map_address = (lcd_control & LCDC::WindowTileMapArea) ? 0x9c00 : 0x9800;
+
+		// Tile data
+		// uint32_t tile_data_size = 4096; // 4KiB / 16B = 256 tiles
+		bool tile_data_mode = lcd_control & LCDC::BGandWindowTileDataArea;
+		uint32_t tile_data_address = (tile_data_mode) ? 0x8000 : 0x8800;
+
+		// Pallete
+		uint8_t bg_palette = Emu::the().readMemory(0xff47) & 0xff;
+
+		for (uint32_t i = 0; i < tile_map_size; ++i) {
+			uint8_t tile_index = Emu::the().readMemory(bg_tile_map_address + i);
+			drawTile((i % 32) * TILE_WIDTH, (i / 32) * TILE_HEIGHT, tile_data_address + (tile_index * TILE_SIZE), bg_palette);
+		}
+	}
+
+	auto& scene = Inferno::Application::the().scene();
+	auto texture = std::make_shared<Inferno::Texture>(m_screen.data(), SCREEN_WIDTH, SCREEN_HEIGHT, FORMAT_SIZE);
+	scene.removeComponent<Inferno::SpriteComponent>(m_entity);
+	scene.addComponent<Inferno::SpriteComponent>(m_entity, glm::vec4 { 1.0f }, texture);
+}
+
+void PPU::drawTile(uint32_t x, uint32_t y, uint32_t tile_address, uint8_t bg_palette)
+{
+	uint32_t viewport_x = Emu::the().readMemory(0xff43);
+	uint32_t viewport_y = Emu::the().readMemory(0xff42);
+
+	// Tile is not within viewport
+	if ((x < viewport_x || x > viewport_x + SCREEN_WIDTH)
+	    || (y < viewport_y || y > viewport_y + SCREEN_HEIGHT)) {
+		return;
+	}
+
+	size_t screen_index = ((x - viewport_x) * FORMAT_SIZE) + ((y - viewport_y) * SCREEN_WIDTH * FORMAT_SIZE);
+	for (uint8_t tile_y = 0; tile_y < TILE_SIZE; tile_y += 2) {
+		uint8_t pixels_lsb = Emu::the().readMemory(tile_address + tile_y);
+		uint8_t pixels_msb = Emu::the().readMemory(tile_address + tile_y + 1);
+
+		for (uint8_t tile_x = 0; tile_x < 8; ++tile_x) {
+			size_t index = screen_index + (tile_x * FORMAT_SIZE);
+
+			// FIXME: Tile is partly out of viewport?
+			if (index + 2 >= m_screen.size()) {
+				continue;
+			}
+
+			uint8_t pixel_index = (pixels_lsb >> (7 - tile_x) | ((pixels_msb >> (7 - tile_x)) << 1)) & 0x3;
+			uint8_t pixel_color = (bg_palette >> (pixel_index * 2)) & 0x3;
+
+			if (pixel_color == 0) {
+				m_screen[index + 0] = 255;
+				m_screen[index + 1] = 255;
+				m_screen[index + 2] = 255;
+			}
+			else if (pixel_color == 1) {
+				m_screen[index + 0] = 168;
+				m_screen[index + 1] = 168;
+				m_screen[index + 2] = 168;
+			}
+			else if (pixel_color == 2) {
+				m_screen[index + 0] = 84;
+				m_screen[index + 1] = 84;
+				m_screen[index + 2] = 84;
+			}
+			else if (pixel_color == 3) {
+				m_screen[index + 0] = 0;
+				m_screen[index + 1] = 0;
+				m_screen[index + 2] = 0;
+			}
+		}
+
+		// Move to next line
+		screen_index += SCREEN_WIDTH * FORMAT_SIZE;
+	}
+}

src/ppu.h

@@ -7,27 +7,43 @@
 
 #pragma once
 
+#include <array>
 #include <cstdint> // uint8_t, uint32_t
 
-#include "processing-unit.h"
 #include "ruc/meta/core.h"
 
+#include "processing-unit.h"
+
+#define SCREEN_WIDTH 160
+#define SCREEN_HEIGHT 144
+#define FORMAT_SIZE 3
+#define TILE_WIDTH 8
+#define TILE_HEIGHT 8
+#define TILE_SIZE 16
+
 enum LCDC : uint8_t {
 	None = 0,
 	BGandWindowEnable = BIT(0),
 	OBJEnable = BIT(1),
 	OBJSize = BIT(2),                 // 0 = 8x8, 1 = 8x16
-	BGTileMapArea = BIT(3),           // 0 = 9800-9bff, 1 = 9c00-9fff
-	BGandWindowTileDataArea = BIT(4), // 0 = 8800-97ff, 1 = 8000-8fff
+	BGTileMapArea = BIT(3),           // 0 = 0x9800-9bff, 1 = 0x9c00-9fff
+	BGandWindowTileDataArea = BIT(4), // 0 = 0x8800-97ff, 1 = 0x8000-8fff
 	WindowEnable = BIT(5),            //
-	WindowTileMapArea = BIT(6),       // 0 = 9800-9bff, 1 = 9c00-9fff
+	WindowTileMapArea = BIT(6),       // 0 = 0x9800-9bff, 1 = 0x9c00-9fff
 	LCDandPPUEnable = BIT(7),
 };
 
 class PPU final : public ProcessingUnit {
 public:
 	PPU(uint32_t frequency);
-	virtual ~PPU();
+	~PPU();
+
+	void update() override;
+	void render();
+
+	void drawTile(uint32_t screen_x, uint32_t screen_y, uint32_t tile_address, uint8_t bg_palette);
 
-	virtual void update() override;
+private:
+	uint32_t m_entity;
+	std::array<uint8_t, SCREEN_WIDTH * FORMAT_SIZE * SCREEN_HEIGHT> m_screen;
 };