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From 90e837ffd1ff5c9add1074d69de23e58a3a4810e Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Date: Wed, 11 Nov 2020 09:26:03 -0500
Subject: [PATCH 1/3] terrain: Fix precision bug in light rendering
Resulting in overly bright rendering when mediump is implemented as
fp16.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
---
data/shaders/terrain.frag | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/data/shaders/terrain.frag b/data/shaders/terrain.frag
index 84d085c..58f17ea 100644
--- a/data/shaders/terrain.frag
+++ b/data/shaders/terrain.frag
@@ -67,7 +67,12 @@ void main() {
vec3 pointSpecular = vec3( 0.0 );
for ( int i = 0; i < MAX_POINT_LIGHTS; i ++ ) {
vec4 lPosition = viewMatrix * vec4( pointLightPosition[ i ], 1.0 );
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+ // should be highp for correct behaviour if mediump is implemented as fp16
+ highp vec3 lVector = lPosition.xyz + vViewPosition.xyz;
+#else
vec3 lVector = lPosition.xyz + vViewPosition.xyz;
+#endif
float lDistance = 1.0;
if ( pointLightDistance[ i ] > 0.0 )
lDistance = 1.0 - min( ( length( lVector ) / pointLightDistance[ i ] ), 1.0 );
From 1edd76fda77edabd49d713912aee49b8360c86c3 Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Date: Wed, 11 Nov 2020 09:49:52 -0500
Subject: [PATCH 2/3] terrain: Fix precision handling in noise shader
Another overflow resulting in infinity in mediump. Note this bug is
masked if the driver clamps infinity to MAX_FLOAT, but it's still our
bug.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
---
data/shaders/terrain-noise.frag | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/data/shaders/terrain-noise.frag b/data/shaders/terrain-noise.frag
index 7fea5c0..9535e58 100644
--- a/data/shaders/terrain-noise.frag
+++ b/data/shaders/terrain-noise.frag
@@ -17,7 +17,13 @@ uniform float time;
uniform MEDIUMP vec2 uvScale;
varying vec2 vUv;
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+// x should be passed as highp since the intermediate multiplications can
+// overflow with mediump
+vec4 permute(highp vec4 x)
+#else
vec4 permute(vec4 x)
+#endif
{
return mod(((x * 34.0) + 1.0) * x, 289.0);
}
From e866cc633ffc450e5358b2742f32ca360e4f3f12 Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Date: Wed, 11 Nov 2020 09:35:21 -0500
Subject: [PATCH 3/3] loop,function,conditionals: Fix mediump overflow
The multiplication can produce infinity.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
---
data/shaders/conditionals.frag | 9 ++++++++-
data/shaders/function.frag | 9 ++++++++-
data/shaders/loop.frag | 9 ++++++++-
3 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/data/shaders/conditionals.frag b/data/shaders/conditionals.frag
index 3bd2507..e902263 100644
--- a/data/shaders/conditionals.frag
+++ b/data/shaders/conditionals.frag
@@ -2,7 +2,14 @@ varying vec4 dummy;
void main(void)
{
- float d = fract(gl_FragCoord.x * gl_FragCoord.y * 0.0001);
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+ // should be declared highp since the multiplication can overflow in
+ // mediump, particularly if mediump is implemented as fp16
+ highp vec2 FragCoord = gl_FragCoord.xy;
+#else
+ vec2 FragCoord = gl_FragCoord.xy;
+#endif
+ float d = fract(FragCoord.x * FragCoord.y * 0.0001);
$MAIN$
diff --git a/data/shaders/function.frag b/data/shaders/function.frag
index 3e3c74f..9d0230e 100644
--- a/data/shaders/function.frag
+++ b/data/shaders/function.frag
@@ -8,7 +8,14 @@ $PROCESS$
void main(void)
{
- float d = fract(gl_FragCoord.x * gl_FragCoord.y * 0.0001);
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+ // should be declared highp since the multiplication can overflow in
+ // mediump, particularly if mediump is implemented as fp16
+ highp vec2 FragCoord = gl_FragCoord.xy;
+#else
+ vec2 FragCoord = gl_FragCoord.xy;
+#endif
+ float d = fract(FragCoord.x * FragCoord.y * 0.0001);
$MAIN$
diff --git a/data/shaders/loop.frag b/data/shaders/loop.frag
index 31ae23e..9a6afd2 100644
--- a/data/shaders/loop.frag
+++ b/data/shaders/loop.frag
@@ -3,7 +3,14 @@ uniform int FragmentLoops;
void main(void)
{
- float d = fract(gl_FragCoord.x * gl_FragCoord.y * 0.0001);
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+ // should be declared highp since the multiplication can overflow in
+ // mediump, particularly if mediump is implemented as fp16
+ highp vec2 FragCoord = gl_FragCoord.xy;
+#else
+ vec2 FragCoord = gl_FragCoord.xy;
+#endif
+ float d = fract(FragCoord.x * FragCoord.y * 0.0001);
$MAIN$
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