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Work around driver bugs on Apple Radeon GPUs

This commit is contained in:
Patrick Walton 2017-02-07 14:39:36 -08:00
parent 4be3938ab7
commit e9fd5d6b1b
2 changed files with 23 additions and 7 deletions
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14
resources/shaders/draw.tcs.glsl
View File

@ -24,8 +24,16 @@ patch out vec2 vpP0;
patch out vec2 vpP1;
// The endpoint of this segment.
patch out vec2 vpP2;
// 1.0 if this segment runs left to right; -1.0 otherwise.
patch out float vpDirection;
// x: 1.0 if this segment runs left to right; -1.0 otherwise.
// y: The tessellation level.
//
// This is packed together into a single vec2 to work around an Apple Intel driver bug whereby
// patch outputs beyond the first 4 are forced to 0.
//
// And in case you're wondering why the tessellation level is passed along in a patch out instead
// of having the TES read it directly, that's another Apple bug workaround, this time in the Radeon
// driver.
patch out vec2 vpDirectionTessLevel;
void main() {
vec2 p0 = gl_in[0].gl_Position.xy;
@ -111,6 +119,6 @@ void main() {
vpP0 = p0;
vpP1 = p1;
vpP2 = p2;
vpDirection = direction;
vpDirectionTessLevel = vec2(direction, tessLevel);
}

16
resources/shaders/draw.tes.glsl
View File

@ -21,8 +21,16 @@ patch in vec2 vpP0;
patch in vec2 vpP1;
// The endpoint of this segment.
patch in vec2 vpP2;
// 1.0 if this segment runs left to right; -1.0 otherwise.
patch in float vpDirection;
// x: 1.0 if this segment runs left to right; -1.0 otherwise.
// y: The tessellation level.
//
// This is packed together into a single vec2 to work around an Apple Intel driver bug whereby
// patch outputs beyond the first 4 are forced to 0.
//
// And in case you're wondering why the tessellation level is passed along in a patch out instead
// of having the TES read it directly, that's another Apple bug workaround, this time in the Radeon
// driver.
patch in vec2 vpDirectionTessLevel;
// The starting point of the segment.
flat out vec2 vP0;
@ -38,7 +46,7 @@ flat out vec2 vYMinMax;
void main() {
// Work out how many lines made up this segment, which line we're working on, and which
// endpoint of that line we're looking at.
uint tessPointCount = uint(gl_TessLevelInner[0] + 1.0f);
uint tessPointCount = uint(vpDirectionTessLevel.y + 1.0f);
uint tessIndex = uint(round(gl_TessCoord.x * float(tessPointCount - 1)));
uint lineCount = tessPointCount / 2, lineIndex = tessIndex / 2, endpoint = tessIndex % 2;
@ -59,7 +67,7 @@ void main() {
vSlope = (vP1.y - vP0.y) / (vP1.x - vP0.x);
// Forward direction onto the fragment shader.
vDirection = vpDirection;
vDirection = vpDirectionTessLevel.x;
// Compute our final position in atlas space, rounded out to the next pixel.
float x = endpoint == 0 ? floor(vP0.x) : ceil(vP1.x);