question about multitexturing using opengl slang

OpenGL Development JOGL Development
#1

Hello!

I created this shaders:
vertex shader:
attribute float texturesin1;
attribute float texturesin2;
attribute float texturesin3;
attribute float texturesin4;
varying float texturesout1;
varying float texturesout2;
varying float texturesout3;
varying float texturesout4;
void main(void)
{
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_TexCoord[1] = gl_MultiTexCoord1;
gl_TexCoord[2] = gl_MultiTexCoord2;
gl_TexCoord[3] = gl_MultiTexCoord3;
texturesout1 = texturesin1;
texturesout2 = texturesin2;
texturesout3 = texturesin3;
texturesout4 = texturesin4;
}

fragment shader:
uniform sampler2D deeptexture;
uniform sampler2D lowtexture;
uniform sampler2D hightexture;
uniform sampler2D toptexture;
varying float texturesout1;
varying float texturesout2;
varying float texturesout3;
varying float texturesout4;
void main (void)
{
vec4 deep = texture2D(deeptexture, gl_TexCoord[0].st );
vec4 low = texture2D(lowtexture, gl_TexCoord[1].st );
vec4 high = texture2D(hightexture, gl_TexCoord[2].st );
vec4 top = texture2D(toptexture, gl_TexCoord[3].st );
vec4 newcolor =
texturesout1 * deep +
texturesout2 * low +
texturesout3 * high +
texturesout4 * top;
gl_FragColor = newcolor;
}

This shader helps me to draw a terrain with 4 textures depending on high. I compute the texture combination values, and I pass it to the vertex shader. THe values are stored in a vertex buffer object.
My problem is, that if I pass the textureout values through the vertex shader, and I want to use it in the framgent shader, it is extremely slow (0.1fps). When I use a constant value in the framgent shader, it is running with 400fps.

How can I fix this problem?
thanks.

#2

Hi,

I dont know if its going to do any difference but how about trying to use vec4 to store all those alpha values in just one attribute and varying variable.
Then you create one bufferobject to store vec4 values for each vertex. That might be faster.


attribute vec4 texAlphas;
varying vec4 texAlphasOut;
...
texAlphasOut = texAlphas;
  • nG
#3

It’s working! I used vec4 attribute with vbo.

Thanks.