add transparency

2 files changed, 218 insertions, 11 deletions

diff --git a/examples/transparency.c b/examples/transparency.c
new file mode 100644
index 0000000..c12ea93
--- /dev/null
+++ b/examples/transparency.c
@@ -0,0 +1,188 @@
+#include <math.h>
+#include <stdlib.h>
+
+#include "../sponge.h"
+#define SPONGE_EXAMPLE_IMPLEMENTATION
+#define SPONGE_EXAMPLE_INIT_DEFINED
+#define SPONGE_EXAMPLE_MOUSE_MOVE_DEFINED
+#define SPONGE_EXAMPLE_DRAW_FRAME_3D_DEFINED
+#include "example.h"
+
+#define FOV (60.0f / PI * 2.0f)
+#define DISTANCE (10.0f)
+#define GOLDEN_RATIO (1.618033988749f)
+
+static int32_t mouse_x;
+static int32_t mouse_y;
+
+static sponge_Vec3    positions[12];
+static sponge_Color32 colors[12];
+static sponge_Color32 colors_red[12];
+static sponge_Color32 colors_green[12];
+static sponge_Color32 colors_blue[12];
+static int32_t        triangles[20 * 3];
+
+void make_icosahedron(sponge_Vec3 out_positions[12], int32_t out_triangles[20 * 3]) {
+    float a = sqrtf(1.0f / (1.0f + (GOLDEN_RATIO * GOLDEN_RATIO)));
+    float b = a * GOLDEN_RATIO;
+    out_positions[0]  = sponge_vec3_make(0.0f, -a,  b);
+    out_positions[1]  = sponge_vec3_make(0.0f,  a,  b);
+    out_positions[2]  = sponge_vec3_make(0.0f, -a, -b);
+    out_positions[3]  = sponge_vec3_make(0.0f,  a, -b);
+
+    out_positions[4]  = sponge_vec3_make(-b, 0.0f,  a);
+    out_positions[5]  = sponge_vec3_make( b, 0.0f,  a);
+    out_positions[6]  = sponge_vec3_make(-b, 0.0f, -a);
+    out_positions[7]  = sponge_vec3_make( b, 0.0f, -a);
+
+    out_positions[8]  = sponge_vec3_make(-a,  b, 0.0f);
+    out_positions[9]  = sponge_vec3_make( a,  b, 0.0f);
+    out_positions[10] = sponge_vec3_make(-a, -b, 0.0f);
+    out_positions[11] = sponge_vec3_make( a, -b, 0.0f);
+
+    size_t i = 0;
+    // 2x y
+    out_triangles[i++] =  4; out_triangles[i++] =  1; out_triangles[i++] =  0;
+    out_triangles[i++] =  0; out_triangles[i++] =  1; out_triangles[i++] =  5;
+    out_triangles[i++] =  3; out_triangles[i++] =  2; out_triangles[i++] =  7;
+    out_triangles[i++] =  2; out_triangles[i++] =  3; out_triangles[i++] =  6;
+    // 2y z
+    out_triangles[i++] =  4; out_triangles[i++] =  6; out_triangles[i++] =  8;
+    out_triangles[i++] = 10; out_triangles[i++] =  6; out_triangles[i++] =  4;
+    out_triangles[i++] =  7; out_triangles[i++] =  5; out_triangles[i++] =  9;
+    out_triangles[i++] =  5; out_triangles[i++] =  7; out_triangles[i++] = 11;
+    // 2z x
+    out_triangles[i++] =  8; out_triangles[i++] =  9; out_triangles[i++] =  1;
+    out_triangles[i++] =  3; out_triangles[i++] =  9; out_triangles[i++] =  8;
+    out_triangles[i++] =  0; out_triangles[i++] = 11; out_triangles[i++] = 10;
+    out_triangles[i++] = 10; out_triangles[i++] = 11; out_triangles[i++] =  2;
+    // xyz
+    out_triangles[i++] = 10; out_triangles[i++] =  4; out_triangles[i++] =  0;
+    out_triangles[i++] =  0; out_triangles[i++] =  5; out_triangles[i++] = 11;
+    out_triangles[i++] =  1; out_triangles[i++] =  4; out_triangles[i++] =  8;
+    out_triangles[i++] =  9; out_triangles[i++] =  5; out_triangles[i++] =  1;
+    out_triangles[i++] =  2; out_triangles[i++] =  6; out_triangles[i++] = 10;
+    out_triangles[i++] = 11; out_triangles[i++] =  7; out_triangles[i++] =  2;
+    out_triangles[i++] =  8; out_triangles[i++] =  6; out_triangles[i++] =  3;
+    out_triangles[i++] =  3; out_triangles[i++] =  7; out_triangles[i++] =  9;
+}
+
+// NOTE(kard):
+// there are many ways to handle opacity and base library doesn't provide one.
+// this example implementation requires caller to order objects back to front.
+// you could allocate multiple canvases and merge them at the end (after sorting pixel based on depth).
+void draw_mesh_col_transparent(
+    sponge_Texture c, float *depths,
+    sponge_Mat4 model, sponge_Mat4 view, sponge_Mat4 proj,
+    sponge_Vec3 *positions, sponge_Color32 *colors, int32_t *triangles, size_t triangles_count,
+    float opacity
+) {
+    sponge_Mat4 mvp = sponge_mat4_mul_mat4(sponge_mat4_mul_mat4(model, view), proj);
+    for (size_t i = 0; i < triangles_count; i += 3) {
+        sponge_DrawMeshTriangleContext ctx = sponge_draw_mesh_triangle_init(c, mvp, positions, triangles, i);
+        sponge_Color32 *row = c.pixels + (ctx.min_pixel.y * c.stride_pixels);
+        float *depth_row = depths + (ctx.min_pixel.y * c.stride_pixels);
+
+        for (int32_t y = ctx.min_pixel.y; y <= ctx.max_pixel.y; y++, row += c.stride_pixels, depth_row += c.stride_pixels) {
+            for (int32_t x = ctx.min_pixel.x; x <= ctx.max_pixel.x; x++) {
+                float w0, w1, w2;
+                if (sponge_draw_mesh_triangle_iter(ctx, sponge_vec2i_make(x, y), &depth_row[x], &w0, &w1, &w2)) {
+                    sponge_ColorF c0 = sponge_color32_to_colorf(colors[ctx.t0]);
+                    sponge_ColorF c1 = sponge_color32_to_colorf(colors[ctx.t1]);
+                    sponge_ColorF c2 = sponge_color32_to_colorf(colors[ctx.t2]);
+                    sponge_ColorF result = sponge_vec4_make(0.0f, 0.0f, 0.0f, 0.0f);
+                    result = sponge_vec4_add(result, sponge_vec4_mul(c0, w0));
+                    result = sponge_vec4_add(result, sponge_vec4_mul(c1, w1));
+                    result = sponge_vec4_add(result, sponge_vec4_mul(c2, w2));
+
+                    sponge_ColorF cur = sponge_color32_to_colorf(row[x]);
+                    result = sponge_vec4_add(cur, sponge_vec4_mul(sponge_vec4_sub(result, cur), opacity));
+                    row[x] = sponge_colorf_to_color32(result);
+                }
+            }
+        }
+    }
+}
+
+void init() {
+    make_icosahedron(positions, triangles);
+    sponge_Vec3 light = sponge_vec3_make(1.0f, 1.0f, 1.0f);
+    float len = (light.x * light.x) + (light.y * light.y) + (light.z * light.z);
+    len = sqrtf(len);
+    light = sponge_vec3_mul(light, 1.0f / len);
+    for (uint32_t i = 0; i < 12; i++) {
+        sponge_Vec3 v = positions[i];
+        float value = v.x * light.x + v.y * light.y + v.z * light.z;
+        value = SPONGE_CLAMP(value, 0.1f, 1.0f);
+        sponge_ColorF color = sponge_vec4_make(1.0f, value, value, value);
+        color = sponge_vec4_mul(color, 255.0f);
+        colors[i] = sponge_colorf_to_color32(color);
+        colors_red[i] = sponge_color32_make(0xFFFF0000);
+        colors_green[i] = sponge_color32_make(0xFF00FF00);
+        colors_blue[i] = sponge_color32_make(0xFF0000FF);
+
+        //sponge_Vec3 v = sponge_vec3_mul(positions[i], 255.0f);
+        //colors[i] = sponge_colorf_to_color32(sponge_vec4_make(1.0f, SPONGE_ABS(v.x), SPONGE_ABS(v.y), SPONGE_ABS(v.z)));
+    }
+}
+
+void mouse_move(int32_t x, int32_t y) {
+    mouse_x = x;
+    mouse_y = y;
+}
+
+void draw_frame_3d(sponge_Texture c, float *depths) {
+    sponge_clear_3d(c, depths, sponge_color32_make(0xFF000000));
+
+    sponge_Mat4 model = sponge_mat4_translate(2.0f, 0.0f, 0.0f);
+    sponge_Mat4 rotate = sponge_mat4_rotate(0.0f, 90.0f / 360.0f * PI * 2.0f, 0.0f);
+    sponge_Mat4 model_red   = sponge_mat4_mul_mat4(model, rotate);
+    sponge_Mat4 model_green = sponge_mat4_mul_mat4(model_red, rotate);
+    sponge_Mat4 model_blue  = sponge_mat4_mul_mat4(model_green, rotate);
+
+    float rot_y = (float)mouse_x / (float)c.width * PI * 2.0f;
+    float rot_x = ((float)mouse_y / (float)c.height * PI) - (PI * 0.5f);
+    sponge_Mat4 view = sponge_mat4_identity();
+    view = sponge_mat4_mul_mat4(view, sponge_mat4_rotate(rot_x, rot_y, 0.0f));
+    view = sponge_mat4_mul_mat4(view, sponge_mat4_translate(0.0f, 0.0f, -10.0f));
+
+    sponge_Mat4 proj = sponge_mat4_projection(FOV, (float)c.width / (float)c.height, 1.0f, 100.0f);
+    sponge_draw_mesh_col(c, depths, model, view, proj, positions, colors, triangles, 60);
+
+    float z0 = sponge_vec3_mul_mat4(sponge_vec3_make(0.0f, 0.0f, 0.0f), sponge_mat4_mul_mat4(model_red,   view)).z;
+    float z1 = sponge_vec3_mul_mat4(sponge_vec3_make(0.0f, 0.0f, 0.0f), sponge_mat4_mul_mat4(model_green, view)).z;
+    float z2 = sponge_vec3_mul_mat4(sponge_vec3_make(0.0f, 0.0f, 0.0f), sponge_mat4_mul_mat4(model_blue,  view)).z;
+    float z[3] = { z0, z1, z2 };
+    int order[3] = { 0, 1, 2 };
+
+    // do not look at this garbage
+    if (z[order[0]] > z[order[1]]) {
+        int tmp = order[0];
+        order[0] = order[1];
+        order[1] = tmp;
+    }
+    if (z[order[0]] > z[order[2]]) {
+        int tmp = order[0];
+        order[0] = order[2];
+        order[2] = tmp;
+    }
+    if (z[order[1]] > z[order[2]]) {
+        int tmp = order[1];
+        order[1] = order[2];
+        order[2] = tmp;
+    }
+
+    for (int i = 0; i < 3; i++) {
+        switch(order[i]) {
+            case 0:
+                draw_mesh_col_transparent(c, depths, model_red,   view, proj, positions, colors_red,   triangles, 60, 0.1f);
+                break;
+            case 1:
+                draw_mesh_col_transparent(c, depths, model_green, view, proj, positions, colors_green, triangles, 60, 0.2f);
+                break;
+            case 2:
+                draw_mesh_col_transparent(c, depths, model_blue,  view, proj, positions, colors_blue,  triangles, 60, 0.3f);
+                break;
+        }
+    }
+}
diff --git a/sponge.h b/sponge.h
index f5dcacb..51e1b7d 100644
--- a/sponge.h
+++ b/sponge.h
@@ -61,9 +61,13 @@ sponge_Vec2I sponge_vec2i_make(int32_t x, int32_t y);
 sponge_Vec2 sponge_vec2_add(sponge_Vec2 v0, sponge_Vec2 v1);
 sponge_Vec2 sponge_vec2_sub(sponge_Vec2 v0, sponge_Vec2 v1);
 sponge_Vec2 sponge_vec2_mul(sponge_Vec2 v0, float f);
-float       sponge_vec2_dot(sponge_Vec2 v0, sponge_Vec2 v1);
+
+sponge_Vec3 sponge_vec3_add(sponge_Vec3 v0, sponge_Vec3 v1);
+sponge_Vec3 sponge_vec3_sub(sponge_Vec3 v0, sponge_Vec3 v1);
+sponge_Vec3 sponge_vec3_mul(sponge_Vec3 v0, float f);
 
 sponge_Vec4 sponge_vec4_add(sponge_Vec4 v0, sponge_Vec4 v1);
+sponge_Vec4 sponge_vec4_sub(sponge_Vec4 v0, sponge_Vec4 v1);
 sponge_Vec4 sponge_vec4_mul(sponge_Vec4 v0, float f);
 
 sponge_ColorF  sponge_color32_to_colorf(sponge_Color32 col);
@@ -230,10 +234,18 @@ sponge_Vec2 sponge_vec2_sub(sponge_Vec2 v0, sponge_Vec2 v1) {
 sponge_Vec2 sponge_vec2_mul(sponge_Vec2 v0, float f) {
     return (sponge_Vec2){ .x = v0.x * f, .y = v0.y * f };
 }
-float       sponge_vec2_dot(sponge_Vec2 v0, sponge_Vec2 v1) {
-    return (v0.x * v1.x) + (v0.y * v1.y);
+
+sponge_Vec3 sponge_vec3_add(sponge_Vec3 v0, sponge_Vec3 v1) {
+    return (sponge_Vec3){ .x = v0.x + v1.x, .y = v0.y + v1.y, .z = v0.z + v1.z };
+}
+sponge_Vec3 sponge_vec3_sub(sponge_Vec3 v0, sponge_Vec3 v1) {
+    return (sponge_Vec3){ .x = v0.x - v1.x, .y = v0.y - v1.y, .z = v0.z - v1.z };
+}
+sponge_Vec3 sponge_vec3_mul(sponge_Vec3 v0, float f) {
+    return (sponge_Vec3){ .x = v0.x * f, .y = v0.y * f, .z = v0.z * f };
 }
 
+
 sponge_ColorF  sponge_color32_to_colorf(sponge_Color32 col) {
     return (sponge_ColorF){ .a = (float)col.a, .r = (float)col.r, .g = (float)col.g, .b = (float)col.b };
 }
@@ -242,17 +254,24 @@ sponge_Color32 sponge_colorf_to_color32(sponge_ColorF  col) {
 }
 
 sponge_Vec4 sponge_vec4_add(sponge_Vec4 v0, sponge_Vec4 v1) {
-    v0.a += v1.a;
-    v0.r += v1.r;
-    v0.g += v1.g;
-    v0.b += v1.b;
+    v0.x += v1.x;
+    v0.y += v1.y;
+    v0.z += v1.z;
+    v0.w += v1.w;
+    return v0;
+}
+sponge_Vec4 sponge_vec4_sub(sponge_Vec4 v0, sponge_Vec4 v1) {
+    v0.x -= v1.x;
+    v0.y -= v1.y;
+    v0.z -= v1.z;
+    v0.w -= v1.w;
     return v0;
 }
 sponge_Vec4 sponge_vec4_mul(sponge_Vec4 v0, float f) {
-    v0.a *= f;
-    v0.r *= f;
-    v0.g *= f;
-    v0.b *= f;
+    v0.x *= f;
+    v0.y *= f;
+    v0.z *= f;
+    v0.w *= f;
     return v0;
 }