Question

I have a textured object in my OpenGL ES scene (version 1.1) for which I want to change the alpha to 0.5.

I am trying the following code :

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glEnable(GL_BLEND); 
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
glColor4f(1.0, 1.0, 1.0, 0.5);

glVertexPointer(3, GL_FLOAT, 0, vertexes);
glNormalPointer(GL_FLOAT, 0, normals);
glTexCoordPointer(2, GL_FLOAT, 0, textures);

GLfloat ambientAndDiffuse[] = kAmbience;
glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, ambientAndDiffuse);
GLfloat specular[] = kSpecular;
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, specular);
glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, kShininess);
GLfloat emission[] = kEmission;
glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, emission);

glDrawElements(GL_TRIANGLES, vertexCount, GL_UNSIGNED_SHORT, indices);

glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_BLEND);

The problem is that the transparency of the model is not changing. The model is displayed on the screen correctly, however the alpha is still 1.

EDIT

My textures are jpgs. Do I need to save these as PNGs ?

Can anyone spot how I can correct this ?

Thank you.

Answer 1

Ah think I’ve solved it – you need to turn off the lighting and then it seems to work.

glDisable(GL_LIGHTING);