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Plan/phaseI.md

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+# Phase 1: C-Based GPU Emulator (3–4 Months)
+
+**Objective**: Build a minimal GPU emulator in C, linked against PortableGL, to simulate a basic rendering pipeline with a command buffer-driven architecture.
+
+**Tasks**:
+- **Proposed Architecture Design**:
+  - Define a `gpu_state` struct containing command buffer, rasterizer state, shader core state, and memory (VRAM, framebuffer).
+  - Design a pure or in-place `tick` function to process commands and update `gpu_state`.
+  - Specify a command buffer format (e.g., tagged union for draw, bind, state commands).
+- **PortableGL Integration**:
+  - Wrap or modify PortableGL to enqueue OpenGL commands (e.g., `glDrawArrays`, `glBindTexture`) into the GPU’s command buffer.
+  - Bypass PortableGL’s rendering pipeline to use the custom GPU model for processing.
+- **Core Components**:
+  - Implement a command processor to dequeue and dispatch commands.
+  - Develop a simple vertex and fragment shader executor (C functions).
+  - Create a rasterizer for triangle scan conversion and fragment generation.
+  - Simulate GPU memory as a byte array for vertex buffers, textures, and framebuffer.
+- **Testing**:
+  - Test with PortableGL’s “hello triangle” example to render a single triangle.
+  - Output the framebuffer to a file (e.g., PPM image) for verification.
+- **Documentation**:
+  - Document the C model’s architecture, command buffer format, and PortableGL integration.
+  - Provide setup instructions for building and running the emulator.