aboutsummaryrefslogtreecommitdiffhomepage
diff options
context:
space:
mode:
authorGravatar sfan5 <sfan5@live.de>2018-09-23 00:29:44 +0200
committerGravatar Jan Ekström <jeebjp@gmail.com>2018-09-26 23:53:05 +0300
commita4c5a4486e5897cd6fb5d8136ec1ea031a3e045a (patch)
tree54ed39626756b306498659f827860946e329275d
parent9dbab9661c4ed36dca1b655440a02db37cd92af0 (diff)
vo_gpu: adjust PRNG variant used by GL shaders
Certain low-end Mali GPUs have a rather low precision and overflow during the PRNG calculations, thereby breaking e.g. deband-grain. Modify the permute() to avoid this, this does not impact the quality of PRNG output (noticeably). This problem was observed on: GL_VENDOR='ARM', GL_RENDERER='Mali-T720' GL_VERSION='OpenGL ES 3.1 v1.r15p0-00rel0.bdd9e62cdc8c88e0610a16b5901161e9'
-rw-r--r--video/out/gpu/video_shaders.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/video/out/gpu/video_shaders.c b/video/out/gpu/video_shaders.c
index 2b18d172db..342fb39ded 100644
--- a/video/out/gpu/video_shaders.c
+++ b/video/out/gpu/video_shaders.c
@@ -833,10 +833,14 @@ void pass_color_map(struct gl_shader_cache *sc,
// Wide usage friendly PRNG, shamelessly stolen from a GLSL tricks forum post.
// Obtain random numbers by calling rand(h), followed by h = permute(h) to
// update the state. Assumes the texture was hooked.
+// permute() was modified from the original to avoid "large" numbers in
+// calculations, since low-end mobile GPUs choke on them (overflow).
static void prng_init(struct gl_shader_cache *sc, AVLFG *lfg)
{
GLSLH(float mod289(float x) { return x - floor(x * 1.0/289.0) * 289.0; })
- GLSLH(float permute(float x) { return mod289((34.0*x + 1.0) * x); })
+ GLSLHF("float permute(float x) {\n");
+ GLSLH(return mod289( mod289(34.0*x + 1.0) * (fract(x) + 1.0) );)
+ GLSLHF("}\n");
GLSLH(float rand(float x) { return fract(x * 1.0/41.0); })
// Initialize the PRNG by hashing the position + a random uniform