comparison: shader/ellipsis_frag.glsl
shader/ellipsis_frag.glsl
- changeset 173
- bd57fe3f6360
- parent 159
- da7ebfcdd159
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| 172:8178eee19656 | 173:bd57fe3f6360 |
|---|---|
| 1 | |
| 2 layout(location = 0) out vec4 diffuse; | |
| 3 in vec2 uvcoord; | |
| 4 | |
| 5 uniform vec2 radii; | |
| 6 #ifdef FILL | |
| 7 uniform vec4 color; | |
| 8 #endif | |
| 9 #ifdef BORDER | |
| 10 uniform float thickness; | |
| 11 uniform vec4 border_color; | |
| 12 #endif | |
| 13 | |
| 14 void main(void) { | |
| 15 // Calculate center of the ellipse | |
| 16 vec2 center = radii; | |
| 17 | |
| 18 // Calculate position relative to center | |
| 19 vec2 pos = uvcoord - center; | |
| 20 | |
| 21 // For an ellipse, we need to calculate normalized distance based on the formula: | |
| 22 // (x/a)² + (y/b)² = 1 where a and b are the semi-axes | |
| 23 vec2 normalized = pos / center; | |
| 24 | |
| 25 // Calculate squared distance in ellipse space | |
| 26 // Value = 1.0 exactly at the ellipse boundary | |
| 27 float dist_squared = dot(normalized, normalized); | |
| 28 | |
| 29 #ifndef BORDER | |
| 30 // For filled ellipse | |
| 31 if (dist_squared > 1.0) { | |
| 32 discard; // Outside the ellipse | |
| 33 } | |
| 34 diffuse = color; | |
| 35 #else // BORDER | |
| 36 // For outlined ellipse | |
| 37 // Calculate inner border threshold based on thickness | |
| 38 // We need to determine the inner ellipse boundary | |
| 39 float border_ratio = thickness / min(center.x, center.y); | |
| 40 | |
| 41 // The inner ellipse has a smaller radius but follows the same equation | |
| 42 // We need to calculate what normalized value corresponds to the inner ellipse | |
| 43 float inner_threshold = 1.0 - border_ratio; | |
| 44 inner_threshold = inner_threshold * inner_threshold; // Square it because we're comparing to dist_squared | |
| 45 | |
| 46 if (dist_squared > 1.0) { | |
| 47 discard; // Outside the ellipse | |
| 48 } else if (dist_squared > inner_threshold) { | |
| 49 // In the border region | |
| 50 diffuse = border_color; | |
| 51 } else { | |
| 52 // Inside the outline | |
| 53 #ifdef FILL | |
| 54 diffuse = color; | |
| 55 #else | |
| 56 discard; | |
| 57 #endif | |
| 58 } | |
| 59 #endif // BORDER | |
| 60 } |
