Add testing depth shader

src/shader/depth_shader.c

@@ -0,0 +1,33 @@
+#include "depth_shader.h"
+#include "constants.h"
+#include "img.h"
+#include "shader.h"
+#include "utils.h"
+
+VertexData depth_shader_vertex(void *shader, const VertexData *vert, u8 index,
+                               const Model *model) {
+  DepthShader *shdr = (DepthShader *)shader;
+
+  V4f vh = V3_to_V4(vert->position);
+  vh.y   = 0.0 - vh.y;
+  vh     = mat4x4_mul_vec4(shdr->final, vh);
+  shdr->vertices[index].position = project_vec4(vh);
+
+  return shdr->vertices[index];
+}
+
+FragmentResult depth_shader_fragment(void *shader, const V3f *barycentric,
+                                     const Colour *colour, const Model *model) {
+  DepthShader *shdr = (DepthShader *)shader;
+
+  // clang-format off
+  M3x3f pos_mat = {.rows = {shdr->vertices[0].position, shdr->vertices[1].position, shdr->vertices[2].position}};
+  pos_mat       = mat3x3_transpose(pos_mat);
+  // clang-format on
+
+  V3f position  = mat3x3_mul_vec3(pos_mat, (*barycentric));
+  f32 channel   = clamp(position.z + DEPTH_MAX, 0.0f, DEPTH_MAX);
+  Colour output = {.r = (u8)(channel), .g = (u8)(channel), .b = (u8)(channel), .a = 255};
+
+  return (FragmentResult){.colour = output};
+}

src/shader/depth_shader.h

@@ -0,0 +1,18 @@
+#ifndef DEPTH_SHADER_H
+#define DEPTH_SHADER_H
+
+#include "constants.h"
+#include "shader.h"
+#include "vec.h"
+
+typedef struct depth_shader DepthShader;
+struct depth_shader {
+#include "shader_base.inc"
+};
+
+VertexData depth_shader_vertex(void *shader, const VertexData *vert, u8 index,
+                               const Model *model);
+FragmentResult depth_shader_fragment(void *shader, const V3f *barycentric,
+                                     const Colour *colour, const Model *model);
+
+#endif // !DEPTH_SHADER_H