rounded quads baby!

resources/shaders/source/rect.frag.glsl

@@ -1,9 +1,55 @@
 #version 450
 
-layout(location = 0) in vec4 col;
+layout(location = 0) in vec4 color;
+layout(location = 1) in vec2 local_position;
+layout(location = 2) in vec2 global_position;
+layout(location = 3) in float radius;
+
 layout(location = 0) out vec4 fragColor;
 
+// SDF for a rounded rectangle given the centerpoint, half size and radius, all in pixels
+float sdf_rr(vec2 p, vec2 center, vec2 half_size, float radius) {
+    // Translate fragment position to rectangle's coordinate system
+    p -= center;
+    // Adjust for rounded corners: shrink the rectangle by the radius
+    vec2 q = abs(p) - half_size + radius;
+    // Combine distance components:
+    // - max(q, 0.0) handles regions outside the rounded corners
+    // - min(max(q.x, q.y), 0.0) handles regions inside the rectangle
+    return length(max(q, 0.0)) + min(max(q.x, q.y), 0.0) - radius;
+}
+
 void main()
 {
-	fragColor = col;
+    // local_position are normalized coordinates in the rectangle, passed from the
+    // vertex shader
+    /*
+     * Window
+     * +-----------------------+
+     * |              (1,1)    |
+     * |     +----------x      |
+     * |     |          |      |
+     * |     |          |      |
+     * |     |   Rect   |      |
+     * |     |          |      |
+     * |     |          |      |
+     * |     x----------+      |
+     * |  (-1,-1)              |
+     * |                       |
+     * +-----------------------+
+     */ 
+
+    vec2 dx = dFdx(local_position);
+    vec2 dy = dFdy(local_position);
+    // Conversion from normalized coordinates to pixels
+    vec2 norm_to_px = 1.0 / vec2(length(dx), length(dy));
+	
+    vec2 centerpoint = global_position - local_position * norm_to_px;
+    // the half size of the rectangle is also norm_to_px
+    vec2 half_size = 1.0 * norm_to_px;
+
+    float distance = sdf_rr(global_position, centerpoint, half_size, radius);
+    float alpha = 1.0 - smoothstep(0.0, 1.0, max(distance, 0.0));
+
+	fragColor = vec4(color.rgb, color.a * alpha);
 }

resources/shaders/source/rect.vert.glsl

@@ -10,6 +10,9 @@ layout(location = 1) in ivec2 uv;
 layout(location = 2) in ivec4 color;
 
 layout(location = 0) out vec4 col;
+layout(location = 1) out vec2 local_position;
+layout(location = 2) out vec2 global_position;
+layout(location = 3) out float radius;
 
 void main()
 {
@@ -24,5 +27,10 @@ void main()
 	pos.y = -(float(position.y)*2.0 / view.y - 1.0);
 
 	gl_Position = vec4(pos+shift, 0.0, 1.0);
+
+	local_position = vec2(sign(uv));
+	global_position = gl_Position.xy;
+	radius = abs(float(uv.x));
+	
 	col = vec4(color) / 255.0;
 }

src/renderer.c3

@@ -566,7 +566,7 @@ fn bool Renderer.push_sprite(&self, short x, short y, short w, short h, short u,
 }
 
 // Push a quad into the quad buffer, return true on success and false on failure
-fn bool Renderer.push_quad(&self, short x, short y, short w, short h, uint color)
+fn bool Renderer.push_quad(&self, short x, short y, short w, short h, uint color, ushort radius = 0)
 {
 	if (self.quad_buffer.count >= MAX_QUAD_BATCH) {
 		return false;
@@ -600,11 +600,14 @@ fn bool Renderer.push_quad(&self, short x, short y, short w, short h, uint color
 	 * |/            |
 	 * +-------------+
 	 * v2            v3
-	 */	
-	quad.vertices.v1 = {.pos = {.x = x,   .y = y},   .col.u = color};
-	quad.vertices.v2 = {.pos = {.x = x,   .y = y+h}, .col.u = color};
-	quad.vertices.v3 = {.pos = {.x = x+w, .y = y+h}, .col.u = color};
-	quad.vertices.v4 = {.pos = {.x = x+w, .y = y},   .col.u = color};
+	 */
+	// the wanted radius is pushed into the uv coordinates, the vertex shader then extracts the absolute value
+	// and passes it to the fragment shader, then it uses the sign to give the fragment shader local coordinates
+	// into the quad.
+	quad.vertices.v1 = {.pos = {.x = x,   .y = y},   .uv = {.u = -radius, .v = +radius}, .col.u = color};
+	quad.vertices.v2 = {.pos = {.x = x,   .y = y+h}, .uv = {.u = -radius, .v = -radius}, .col.u = color};
+	quad.vertices.v3 = {.pos = {.x = x+w, .y = y+h}, .uv = {.u = +radius, .v = -radius}, .col.u = color};
+	quad.vertices.v4 = {.pos = {.x = x+w, .y = y},   .uv = {.u = +radius, .v = +radius}, .col.u = color};
 	// triangle 1 indices
 	quad.indices.i1 = 0; // v1
 	quad.indices.i2 = 1; // v2

test_renderer.c3

@@ -62,7 +62,7 @@ fn int main()
 		}
 
 		// rect 1
-		ren.push_quad(100,100,100,100,0xff00ff00);
+		ren.push_quad(100,100,100,100,0xff00ff00, 20);
 		// rect 2
 		ren.push_quad(0,0,20,20,0xff0000ff);
 		// rect 3