Can not access Texture Unit2

OpenGL
1

i tried to write a simple shader which display a texture. if the texture ist stored in Texture Unit1 everything is ok but if the texture is stored in Texture Unit 2 my object is simply black.

The Vertex Shader

varying vec2 texCoords1;
varying vec2 texCoords2;

void main()
{
	gl_Position = ftransform();
	texCoords1 = gl_MultiTexCoord0.st;
	texCoords2 = gl_MultiTexCoord1.st;
}

The Fragment Shader

uniform sampler2D tex1;
uniform sampler2D tex2;

varying vec2 texCoords1;
varying vec2 texCoords2;

void main()
{
gl_FragColor = texture2D(tex2, texCoords2);
}

the texCoords2 vector contain the right values. i display it as a output color

gl_FragColor= vec4(texCoords2,0, 0);

and i get a gradient which make sense.

has anybody an idea whats the problem is?

thanks for your efforts

2

Looks ok to me. Checked you actually set up the uniform samplers correctly? Maybe you can post your application code for setting up the textures and the uniforms?

3

I use openscenegraph and i set up the texture like this

...
Geometry->setTexCoordArray(1,texcoords);
...
osg::StateSet* stateOne = new osg::StateSet();

stateOne->setTextureAttributeAndModes
(1,FaceTexture,osg::StateAttribute::ON);

to store the texture to Texture Unit 2 but i can’t see any texture.

If i set up the texture like this and use the Texture Unit 1 in the shader everything is ok

...
Geometry->setTexCoordArray(0,texcoords);
...
osg::StateSet* stateOne = new osg::StateSet();

stateOne->setTextureAttributeAndModes
(0,FaceTexture,osg::StateAttribute::ON);
4

you need to call glActiveTexture / glClientActiveTexture before binding.

http://www.khronos.org/opengles/documentation/opengles1_0/html/glActiveTexture.html

5

but this happend if i call the

stateOne->setTextureAttributeAndModes
      (1,FaceTexture,osg::StateAttribute::ON);

or not?

6

I have only do multitexturing with OpenSceneGraph with the fixed function pipeline of OpenGL. Did you set your sampler correctly? Look at this link.

Hope that help.

7

By default, the driver/compiler sees you don’t use tex1, so it expects tex2=TexUnit0.
Either you use glUniform1i() to set the sampler to use a given texunit, or on nVidia cards you specify a semantic (which binds the tex2 to a given unit)
uniform sampler2D tex1: TEXUNIT0;
uniform sampler2D tex2: TEXUNIT1;

8

i tried to write a simple shader which display a texture. if the texture ist stored in Texture Unit1 everything is ok but if the texture is stored in Texture Unit 2 my object is simply black

Are you using an Intel driver/card? I’ve found similar problems on shaders that use tha second TU, especially with texture coordinates…

9

By default, the driver/compiler sees you don’t use tex1, so it expects tex2=TexUnit0.

If i also use the tex1 the same thing happened. I see no texture.

I have a gforce 8800 gt but unfortunately
uniform sampler2D tex1: TEXUNIT0;
uniform sampler2D tex2: TEXUNIT1;

don’t work.

Now i have set the sampler and it works. :slight_smile:
Is it necessary to set the sampler if i use TEXUNIT1 or do multitexturing because I don’t set the sampler before

10

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