olemd/tilt-shift-camera
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Fix aspect ratio correction for intermediate rotation angles

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Apply screen aspect ratio correction to offset.y (screen X direction)
instead of offset.x (screen Y direction) in both linear and radial
mode distance calculations. This fixes angle distortion at non-90°
rotations in portrait mode.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Ole-Morten Duesund 2026-01-29 16:57:01 +01:00
commit a3ce90a2fe
1 changed files with 10 additions and 3 deletions
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13
app/src/main/res/raw/tiltshift_fragment.glsl
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@ -29,6 +29,12 @@ float linearFocusDistance(vec2 uv) {
vec2 center = vec2(uPositionY, 1.0 - uPositionX); vec2 center = vec2(uPositionY, 1.0 - uPositionX);
vec2 offset = uv - center; vec2 offset = uv - center;
// Correct for screen aspect ratio to make coordinate space square
// After transform: offset.x = screen Y direction, offset.y = screen X direction
// Scale offset.y to match the scale of offset.x (height units)
float screenAspect = uResolution.x / uResolution.y;
offset.y *= screenAspect;
// Adjust angle by +90 degrees to compensate for the coordinate transformation // Adjust angle by +90 degrees to compensate for the coordinate transformation
// The position transform is a 90° CW rotation, so angles transform as θ + 90° // The position transform is a 90° CW rotation, so angles transform as θ + 90°
float adjustedAngle = uAngle + 1.5707963; float adjustedAngle = uAngle + 1.5707963;
@ -49,10 +55,11 @@ float radialFocusDistance(vec2 uv) {
vec2 center = vec2(uPositionY, 1.0 - uPositionX); vec2 center = vec2(uPositionY, 1.0 - uPositionX);
vec2 offset = uv - center; vec2 offset = uv - center;
// Adjust for aspect ratio to create ellipse // Correct for screen aspect ratio to make coordinate space square
// Correct for screen aspect ratio first // After transform: offset.x = screen Y direction, offset.y = screen X direction
// Scale offset.y to match the scale of offset.x (height units)
float screenAspect = uResolution.x / uResolution.y; float screenAspect = uResolution.x / uResolution.y;
offset.x *= screenAspect; offset.y *= screenAspect;
// Apply rotation // Apply rotation
// Adjust angle by +90 degrees to compensate for the coordinate transformation // Adjust angle by +90 degrees to compensate for the coordinate transformation