feat: add viewport and test

src/main.c

@@ -1,8 +1,38 @@
 #include <stdio.h>
-#include "math/mat4.h"
+#include "cam.h"
+#include "math/vec4.h"
+
+Vec4f_t mat4f_mul_vec4f(const Mat4f_t mat, Vec4f_t v)
+{
+    Vec4f_t out;
+    for (int i = 0; i < 4; i++)
+    {
+        out.data[i] = 0.f;
+        for (int j = 0; j < 4; j++)
+            out.data[i] += mat.m[i*4 + j] * v.data[j];
+    }
+    return out;
+}
 
 int main(int argc, const char** argv)
 {
-    printf("hello world");
+    const float fov = 60;
+    const float width = 1000, height = 800;
+    const float near = 0.1, far = 1000;
+
+    const float aspect = width / height;
+
+    // xyz = [-1, 1]
+    Vec4f_t vec = vec4f(0.f, 0.f, -1.f, 1.f);
+    Mat4f_t proj = perspCam(fov, aspect, near, far);
+
+    Vec4f_t v_clip = mat4f_mul_vec4f(proj, vec);
+
+    normCoord_r(&v_clip);
+    viewport_r(&v_clip, width, height);
+
+    printf("Screen coordinates: x = %f, y = %f, z = %f\n",
+        v_clip.x, v_clip.y, v_clip.z);
+
     return 0;
 }