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workaround for gl_FrontFacing bug

gl_FrontFacing isn't well supported on some Macintosh / ATI combinations.
This commit is contained in:
Tim Moore 2010-06-15 19:29:24 +02:00
parent acac689d59
commit c964caa845
4 changed files with 72 additions and 6 deletions

View file

@ -5,6 +5,7 @@
<texture n ="0">
<type>white</type>
</texture>
<vertex-program-two-side type="bool">false</vertex-program-two-side>
</parameters>
<technique n="10">
<predicate>
@ -60,14 +61,23 @@
</internal-format>
-->
</texture-unit>
<vertex-program-two-side>
<use>vertex-program-two-side</use>
</vertex-program-two-side>
<program>
<vertex-shader>Shaders/model-default.vert</vertex-shader>
<fragment-shader>Shaders/default.frag</fragment-shader>
<fragment-shader>Shaders/model-default.frag</fragment-shader>
</program>
<uniform>
<name>texture</name>
<type>sampler-2d</type>
<value type="int">0</value></uniform>
<name>texture</name>
<type>sampler-2d</type>
<value type="int">0</value>
</uniform>
<uniform>
<name>twoSideHack</name>
<type>bool</type>
<value><use>vertex-program-two-side</use></value>
</uniform>
</pass>
</technique>
<technique n="11">
@ -106,6 +116,10 @@
<mode>modulate</mode>
</environment>
</texture-unit>
<!-- A two-sided lighting model is set by default near the root
of the scene graph. Perhaps that ought to be set in this
effect?
-->
</pass>
</technique>
</PropertyList>

View file

@ -0,0 +1,46 @@
// -*-C++-*-
varying vec4 diffuse, constantColor;
varying vec3 normal, lightDir, halfVector;
varying float fogCoord, alpha;
uniform bool twoSideHack;
uniform sampler2D texture;
float luminance(vec3 color)
{
return dot(vec3(0.212671, 0.715160, 0.072169), color);
}
void main()
{
vec3 n, halfV;
float NdotL, NdotHV, fogFactor;
vec4 color = constantColor;
vec4 texel;
vec4 fragColor;
vec4 specular = vec4(0.0);
n = normalize(normal);
if (twoSideHack && gl_Color.a == 0.0)
n = -n;
NdotL = max(dot(n, lightDir), 0.0);
if (NdotL > 0.0) {
color += diffuse * NdotL;
halfV = normalize(halfVector);
NdotHV = max(dot(n, halfV), 0.0);
if (gl_FrontMaterial.shininess > 0.0)
specular.rgb = (gl_FrontMaterial.specular.rgb
* gl_LightSource[0].specular.rgb
* pow(NdotHV, gl_FrontMaterial.shininess));
}
color.a = alpha;
// This shouldn't be necessary, but our lighting becomes very
// saturated. Clamping the color before modulating by the texture
// is closer to what the OpenGL fixed function pipeline does.
color = clamp(color, 0.0, 1.0);
texel = texture2D(texture, gl_TexCoord[0].st);
fragColor = color * texel + specular;
fogFactor = exp(-gl_Fog.density * gl_Fog.density * fogCoord * fogCoord);
gl_FragColor = mix(gl_Fog.color, fragColor, fogFactor);
}

View file

@ -12,6 +12,8 @@ varying vec4 diffuse, constantColor;
varying vec3 normal, lightDir, halfVector;
varying float alpha, fogCoord;
uniform bool twoSideHack;
void main()
{
vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;
@ -28,6 +30,12 @@ void main()
alpha = gl_FrontMaterial.diffuse.a;
else
alpha = gl_Color.a;
// Another hack for supporting two-sided lighting without using
// gl_FrontFacing in the fragment shader.
if (twoSideHack) {
gl_FrontColor = vec4(0.0, 0.0, 0.0, 1.0);
gl_BackColor = vec4(0.0, 0.0, 0.0, 0.0);
}
constantColor = gl_FrontLightModelProduct.sceneColor
+ gl_FrontMaterial.ambient * gl_LightSource[0].ambient;
fogCoord = abs(ecPosition3.z);

View file

@ -22,8 +22,6 @@ void main()
vec4 specular = vec4(0.0);
n = normalize(normal);
if (!gl_FrontFacing)
n = -n;
NdotL = max(dot(n, lightDir), 0.0);
if (NdotL > 0.0) {
color += diffuse * NdotL;