在Android OpenGL ES 1.1中相乘纹理

Question

I'm trying to learn OpenGL on Android and as part of my learning project I want to make part of a texture transparent. To accomplish that I've got a texture that's all white with the alpha channel set to transparent where I want the transparency. My plan was to multiply this against the texture I want to display, but I'm a little boggled by the abbreviated function names and integer constants.

Any simple but complete examples with texture multiplication out there?

Answer 1

EDIT: my bad, I just saw that you're looking for an gl 1.0 example

Looks like you're looking for a multi-texture example: http://code.google.com/p/opengles-book-samples/source/browse/trunk/Android/Ch10_MultiTexture/src/com/openglesbook/multitexture/MultiTextureRenderer.java?r=45

It's an opengl es 2.0 example. When you read the code, you'll see that the actual blending of the texture is done is in the fragmentshader.

EDIT 2 : I couldn't find a opengl-es 1.1 example, but I have some old opengl 2.0 code lying around. It's in c/c++, so you'll have to convert it to java yourself.

I looked up the GLES 1.1 spec, and it seems it supports the key functions from my code: glActiveTexture, glMultiTexCoord and glTexEnvi, so this may help get you started...

glActiveTextureARB( GL_TEXTURE0_ARB );
glBindTexture( GL_TEXTURE_2D, KdMapIndex );
glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

glActiveTextureARB( GL_TEXTURE1_ARB );
glBindTexture(GL_TEXTURE_2D, KaMapIndex);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_ADD);

glBegin(GL_TRIANGLES);
for (face = faces.begin(); face != faces.end(); face++)
{
    CVector3f normal;
    CVector2f texture0, texture1, texture2;
    CVector3f vertex0, vertex1, vertex2;

    normal.x = data.normals[face->nIndex[0]-1].x;
    normal.y = data.normals[face->nIndex[1]-1].y;
    normal.z = data.normals[face->nIndex[2]-1].z;
    normal.normalize();

    texture0 = data.texcoords[face->tIndex[0]-1];
    texture1 = data.texcoords[face->tIndex[1]-1];
    texture2 = data.texcoords[face->tIndex[2]-1];

    vertex0 = data.vertices[face->vIndex[0]-1];
    vertex1 = data.vertices[face->vIndex[1]-1];
    vertex2 = data.vertices[face->vIndex[2]-1];

    glNormal3f(normal.x, normal.y, normal.z);       // Face normal

    glMultiTexCoord2fARB( GL_TEXTURE0_ARB, texture0.x, texture0.y ); // texcoord 0
    glMultiTexCoord2fARB( GL_TEXTURE1_ARB, texture0.x, texture0.y );        
    glVertex3f(vertex0.x, vertex0.y, vertex0.z);    // vertex 0

    glMultiTexCoord2fARB( GL_TEXTURE0_ARB, texture1.x, texture1.y ); // texcoord 1
    glMultiTexCoord2fARB( GL_TEXTURE1_ARB, texture1.x, texture1.y );    
    glVertex3f(vertex1.x, vertex1.y, vertex1.z);    // vertex 1

    glMultiTexCoord2fARB( GL_TEXTURE0_ARB, texture2.x, texture2.y ); // texcoord 2
    glMultiTexCoord2fARB( GL_TEXTURE1_ARB, texture2.x, texture2.y );    
    glVertex3f(vertex2.x, vertex2.y, vertex2.z);    // vertex 2
}
glEnd();