add rotating cheese

This adds the Cheese3D graphics api and makes the cheese command display a cheese rotating in 3d as a demo

1 files changed, 102 insertions, 0 deletions

diff --git a/stage3/math3d.h b/stage3/math3d.h
new file mode 100644
index 0000000..5d9c759
--- /dev/null
+++ b/stage3/math3d.h
@@ -0,0 +1,102 @@
+#ifndef MATH3D_H
+#define MATH3D_H
+
+#include "math.h"
+
+static inline void mat_id(float mat[4][4])
+{
+	for (int i = 0; i < 4; i++)
+	for (int j = 0; j < 4; j++)
+		mat[i][j] = i == j ? 1.0 : 0.0;
+}
+
+static inline void mat_translate(float mat[4][4], float vec[3])
+{
+	mat_id(mat);
+	for (int i = 0; i < 3; i++)
+		mat[3][i] = vec[i];
+}
+
+static inline void mat_scale(float mat[4][4], float vec[3])
+{
+	mat_id(mat);
+	for (int i = 0; i < 3; i++)
+		mat[i][i] = vec[i];
+}
+
+static inline void mat_rot_x(float mat[4][4], float a)
+{
+	mat_id(mat);
+	mat[1][1] = cos(a); mat[2][1] = -sin(a);
+	mat[1][2] = sin(a); mat[2][2] = cos(a);
+}
+
+static inline void mat_rot_y(float mat[4][4], float a)
+{
+	mat_id(mat);
+	mat[0][0] = cos(a); mat[2][0] = sin(a);
+	mat[0][2] = -sin(a); mat[2][2] = cos(a);
+}
+
+static inline void mat_rot_z(float mat[4][4], float a)
+{
+	mat_id(mat);
+	mat[0][0] = cos(a); mat[1][0] = -sin(a);
+	mat[0][1] = sin(a); mat[1][1] = cos(a);
+}
+
+static inline void mat_copy(float dst[4][4], float src[4][4])
+{
+	for (int i = 0; i < 4; i++)
+	for (int j = 0; j < 4; j++)
+		dst[i][j] = src[i][j];
+}
+
+static inline void mat_mul(float a[4][4], float b[4][4])
+{
+	float out[4][4];
+	for (int i = 0; i < 4; i++)
+	for (int j = 0; j < 4; j++) {
+		out[i][j] = 0;
+		for (int k = 0; k < 4; k++)
+			out[i][j] += a[k][j] * b[i][k];
+	}
+	mat_copy(a, out);
+}
+
+static inline void vec_copy(float dst[4], float src[4])
+{
+	for (int i = 0; i < 4; i++)
+		dst[i] = src[i];
+}
+
+static inline void mat_mul_vec(float mat[4][4], float vec[4])
+{
+	float out[4];
+
+	for (int j = 0; j < 4; j++) {
+		out[j] = 0;
+		for (int k = 0; k < 4; k++)
+			out[j] += mat[k][j] * vec[k];
+	}
+
+	vec_copy(vec, out);
+}
+
+
+static inline void mat_perspective(float mat[4][4], float fov, float aspect, float near, float far)
+{
+	float a = 1.0 / tan(fov / 2.0);
+
+	mat_scale(mat, (float []) { a/aspect, a, -(far + near) / (far - near) });
+	mat[2][3] = -1.0;
+	mat[3][2] = -2.0 * far * near / (far - near);
+	mat[3][3] = 0.0;
+}
+
+static inline float tri_area(float a[2], float b[2], float c[2])
+{
+	return (b[0] - a[0])*(c[1] - a[1]) - (b[1] - a[1])*(c[0] - a[0]);
+}
+
+#endif