Add 3D rotating cube example

ncc/examples/3dcube.c

@@ -0,0 +1,150 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <uvm/syscalls.h>
+#include <uvm/utils.h>
+#include <uvm/3dmath.h>
+#include <uvm/graphics.h>
+
+#define FRAME_WIDTH 800
+#define FRAME_HEIGHT 600
+
+#define remap(v, a0, a1, b0, b1) (b0 + (b1 - b0) * ((v) - a0) / (a1 - a0))
+
+// RGBA pixels
+u32 frame_buffer[FRAME_HEIGHT][FRAME_WIDTH];
+
+// Cube vertices in [-1, 1]
+float verts[8][3] = {
+    {-1.0f, 1.0f, 1.0f },
+    { 1.0f, 1.0f, 1.0f },
+    { 1.0f,-1.0f, 1.0f },
+    {-1.0f,-1.0f, 1.0f },
+    {-1.0f, 1.0f,-1.0f },
+    { 1.0f, 1.0f,-1.0f },
+    { 1.0f,-1.0f,-1.0f },
+    {-1.0f,-1.0f,-1.0f },
+};
+
+vec3 cube_pos = { 0.0f, 0.0f, -6.0f };
+
+float angle = 0.0f;
+
+// Perspective projection matrix
+mat44 persp;
+
+// Translation matrix for the cube
+mat44 trans;
+
+// Rotation matrices for the cube
+mat44 rotx;
+mat44 roty;
+mat44 rot;
+
+mat44 m_cube;
+
+vec3 v_tmp;
+
+vec3 v0;
+vec3 v1;
+
+// Draw a line between two 3D points
+void draw_line3d(vec3 v0, vec3 v1, u32 color)
+{
+    mat44_transform(persp, v0, v_tmp);
+    int x0 = (int)remap(v_tmp[0], -1.0f, 1.0f, 0.0f, (float)FRAME_WIDTH);
+    int y0 = (int)remap(v_tmp[1], -1.0f, 1.0f, 0.0f, (float)FRAME_HEIGHT);
+    //printf("x0=%d, y0=%d\n", x0, y0);
+
+    mat44_transform(persp, v1, v_tmp);
+    int x1 = (int)remap(v_tmp[0], -1.0f, 1.0f, 0.0f, (float)FRAME_WIDTH);
+    int y1 = (int)remap(v_tmp[1], -1.0f, 1.0f, 0.0f, (float)FRAME_HEIGHT);
+
+    // TODO: we should handle coordinates that are outside the screen
+
+    draw_line(
+        (u32*)frame_buffer,
+        FRAME_WIDTH,
+        FRAME_HEIGHT,
+        (u32)x0,
+        (u32)y0,
+        (u32)x1,
+        (u32)y1,
+        color
+    );
+}
+
+void trans_line3d(mat44 trans, vec3 _v0, vec3 _v1)
+{
+    mat44_transform(trans, _v0, v0);
+    mat44_transform(trans, _v1, v1);
+    draw_line3d(v0, v1, COLOR_PURPLE);
+}
+
+void anim_callback()
+{
+    u64 start_time = time_current_ms();
+
+    // Clear the frame buffer, set all pixels to black
+    memset32(frame_buffer, 0, 800 * 600);
+
+    angle = angle + 0.01f;
+
+    mat44_rotx(angle, rotx);
+    mat44_roty(angle, roty);
+
+    mat44_mul(roty, rotx, rot);
+    mat44_mul(rot, trans, m_cube);
+
+    trans_line3d(m_cube, verts[0], verts[1]);
+    trans_line3d(m_cube, verts[1], verts[2]);
+    trans_line3d(m_cube, verts[2], verts[3]);
+    trans_line3d(m_cube, verts[3], verts[0]);
+
+    trans_line3d(m_cube, verts[4], verts[5]);
+    trans_line3d(m_cube, verts[5], verts[6]);
+    trans_line3d(m_cube, verts[6], verts[7]);
+    trans_line3d(m_cube, verts[7], verts[4]);
+
+    trans_line3d(m_cube, verts[0], verts[4]);
+    trans_line3d(m_cube, verts[1], verts[5]);
+    trans_line3d(m_cube, verts[2], verts[6]);
+    trans_line3d(m_cube, verts[3], verts[7]);
+
+    window_draw_frame(0, frame_buffer);
+
+    u64 end_time = time_current_ms();
+    printf("render time: %dms\n", end_time - start_time);
+
+    // Schedule a fixed rate update for the next frame (60fps)
+    fixed_rate_update(start_time, 1000 / 60, anim_callback);
+}
+
+void keydown(u64 window_id, u16 keycode)
+{
+    if (keycode == KEY_ESCAPE)
+    {
+        exit(0);
+    }
+}
+
+int main()
+{
+    window_create(FRAME_WIDTH, FRAME_HEIGHT, "Rotating 3D Cube Example", 0);
+    window_on_keydown(0, keydown);
+    time_delay_cb(0, anim_callback);
+    enable_event_loop();
+
+    // Setup the perspective projection matrix
+    perspective(
+        degtorad(40.0f),
+        (float)FRAME_WIDTH / (float)FRAME_HEIGHT,
+        0.1f,   // near,
+        100.0f, // far,
+        persp
+    );
+
+    mat44_translate(cube_pos, trans);
+
+
+    return 0;
+}

ncc/include/uvm/3dmath.h

@@ -112,7 +112,25 @@ void mat44_translate(vec3 v, mat44 result)
     result[3][2] = v[2];
 }
 
-// Matrix for a rotation about the Y axis
+// Matrix for a rotation around the X axis
+void mat44_rotx(float theta, mat44 result)
+{
+    // Set the matrix to the identity
+    memcpy(result, MAT44_IDENT, sizeof(mat44));
+
+    float cost = cosf(theta);
+    float sint = sinf(theta);
+
+    // Second column
+    result[1][1] = cost;
+    result[1][2] = sint;
+
+    // Third column
+    result[2][1] = -sint;
+    result[2][2] = cost;
+}
+
+// Matrix for a rotation around the Y axis
 void mat44_roty(float theta, mat44 result)
 {
     // Set the matrix to the identity

ncc/include/uvm/graphics.h

@@ -12,7 +12,7 @@
 #define COLOR_ORANGE    0xFF_FF_A5_00
 #define COLOR_YELLOW    0xFF_FF_FF_00
 #define COLOR_MAGENTA   0xFF_FF_00_FF
-#define COLOR_PURPLE    0xFF_CC_88_99
+#define COLOR_PURPLE    0xFF_D6_00_FF
 #define COLOR_TURQUOISE 0xFF_40_E0_D0
 
 // Convert RGB values in the range [0, 255] to a u32 encoding