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.
Ah think I've solved it - you need to turn off the lighting and then it seems to work.
glDisable(GL_LIGHTING);
Have you set the texture environment variable to modulate? Like this:
glTexEnvi (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
That tells OpenGL to multiply the object's color by the texture's color. Also, I don't remember if you need to use a GL_COLOR_ARRY with glDrawElements() instead of just setting the current color.
Related
I have to know how to add color to the rectangle drawn with the below method (which i took from a sample here).. Its by setting the openGL color to some color. But i dont know how to do it. Some help would be appreciated.
-(void) ccDrawFilledRect
{
HelloWorld *gs = [(swipeAppDelegate*)[[UIApplication sharedApplication] delegate] gameScene];
CGPoint poli[]= {gs.StartPoint,CGPointMake(gs.StartPoint.x,gs.EndPoint.y),gs.EndPoint,CGPointMake(gs.EndPoint.x,gs.StartPoint.y)};
glDisable(GL_TEXTURE_2D);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
glVertexPointer(2, GL_FLOAT, 0, poli);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
NSLog(#"openGL rectangles drawn !!");
// restore default state
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnable(GL_TEXTURE_2D);
}
NeHe has a lot of easy OpenGL tutorials. This one is on adding color http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=03 . Make your you have colors and color buffers enabled.
Have you tried putting glColor3d(1, 0, 0) before glVertexPointer?
I've given this a go for a while, but I haven't been able to get favorable results. Basically, I have a sphere with 2 textures. One is blended on top with other and the idea is to have it be a face environment mapping. I want one texture to rotate with the sphere and the other to stay fixed to the initial texture coordinates.
I have tried rotating the GL_TEXTURE matrix of one texture and resetting the other, but this doesn't really do the trick because the texture mapping isn't right when it's rotated certain ways.
Anyone know how i can rotate only one set of texture coordinates and keep the other fixed?
Here's my render code at the moment:
glColor4f(0.0, 0.0, 0.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glClientActiveTexture( GL_TEXTURE0);
glActiveTexture( GL_TEXTURE0);
glBindTexture( GL_TEXTURE_2D, tex[0]);
glEnableClientState( GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, sizeof(TexturedVertexData3D), &SphereVertexData[0].texCoord);
glMatrixMode(GL_TEXTURE);
glPushMatrix();
glTranslatef(0, 0, -4.5f);
glRotatef(.00001, .00001, .0, .0);
glClientActiveTexture( GL_TEXTURE1);
glActiveTexture( GL_TEXTURE1);
glEnable( GL_TEXTURE_2D);
glBindTexture( GL_TEXTURE_2D, tex[1]);
glEnableClientState( GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, sizeof(TexturedVertexData3D), &SphereVertexData[0].texCoord);
glPopMatrix();
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_ADD);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glTranslatef(0, 0, -4.5f);
glVertexPointer(3, GL_FLOAT, sizeof(TexturedVertexData3D), &SphereVertexData[0].vertex);
glNormalPointer(GL_FLOAT, sizeof(TexturedVertexData3D), &SphereVertexData[0].normal);
glDrawArrays(GL_TRIANGLES, 0, kSphereNumberOfVertices);
glPopMatrix();
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
rotation += .0001;
If anyone needs to see more of what is going on just let me know.
You could use two spheres and only issue the glRotatef() to the sphere with the texture that you want rotating. The other sphere would just receive the corresponding glTranslatef() commands. If you are using the alpha channel to blend the textures it should work the same.
I have a texture with transparency (the white triangle with that lighting information), and just can't make it's alpha variable.
alt text http://gotoandplay.freeblog.hu/files/alpha_help.png
The drawing code, with the missing piece:
//Place polygon vertices to the bottom left within the view.
glLoadIdentity();
glTranslatef(centerX, centerY, 0);
//Draw "diffuse" layer.
glBindTexture(GL_TEXTURE_2D, spriteTexture[0]); //Bind.
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
//Offset during development only.
glLoadIdentity();
glTranslatef(centerX-10, centerY+10, 0);
//Draw "specular" layer.
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, spriteTexture[1]); //Bind.
//Some smart alpha scaling code needs here...
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
Could somebody please help me out with the appropriate lines of code?
Some glBlendFunc, or maybe glTextEnvi stuff I suppose.
Ok, I got it even if I don't understand what I did exactly.
//Place polygon vertices to the bottom left within the view.
glLoadIdentity();
glTranslatef(centerX, centerY, 0);
//--1
//Draw "diffuse" layer.
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, spriteTexture[0]); //Bind.
//Blending.
glBlendFunc(GL_ONE, GL_ONE);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
//--2
//Draw "specular" layer.
glBindTexture(GL_TEXTURE_2D, spriteTexture[1]); //Bind.
//Blending.
glColor4f(opacity, opacity, opacity, opacity);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
I tried another way before...
glColor4f(1.0f, 1.0f, 1.0f, opacity);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
...but the second map was somehow "weaker".
I'm trying to overlay one image on top of another onto a simple quad. I set my bottom image as texture unit 0, and then my top image (which has a variable alpha) as texture unit 1. Unit 2 has mode GL_DECAL, which means the bottom texture should show up when the alpha is 0, and the top texture should show when the alpha is 1. But, only the top texture shows up and the bottom one doesn't appear at all. It's just white where the bottom texture should show through.
glGetError() doesn't report any problems. Any help is appreciated. Thanks!
glVertexPointer(3, GL_FLOAT, 0, boxVertices);
glEnableClientState(GL_VERTEX_ARRAY);
glClientActiveTexture(GL_TEXTURE0);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 0, boxTextureCoords);
glClientActiveTexture(GL_TEXTURE1);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 0, boxTextureCoords);
glClientActiveTexture(GL_TEXTURE0);
glEnable(GL_TEXTURE_2D);
glClientActiveTexture(GL_TEXTURE1);
glEnable(GL_TEXTURE_2D);
glClientActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, one.texture);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glClientActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, two.texture);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
Since you're using vertex arrays, you need to use glClientActiveTexture instead of glActiveTexture when setting your texture coords.
I'm working with the iPhone OpenGLES implementation and I wish to endlessly scroll a texture across a simple surface (two triangles making up a rectangle). This should be straightforward, but it's not something I've done before and I must be missing something. I can rotate the texture fine, but translate does not work at all. Do I have a minor implementation issue or am I doing something fundamentally wrong?
// move texture
glMatrixMode(GL_TEXTURE);
glPushMatrix();
glLoadIdentity();
// increment offset - no reset for demo purposes
wallOffset += 1.0;
// move the texture - this does not work
glTranslatef(wallOffset,wallOffset,0.0);
// rotate the texture - this does work
//glRotatef(wallOffset, 1.0, 0.0, 0.0);
glMatrixMode(GL_MODELVIEW);
glBindTexture(GL_TEXTURE_2D, WallTexture.name);
glTexCoordPointer(2, GL_FLOAT, 0, coordinates);
// simple drawing code
glNormalPointer(GL_FLOAT, 0, normals);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
// push matrix back
glMatrixMode(GL_TEXTURE);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
You're incrementing your texture offset by 1.0f; but textures coordinates are considered in the range [0, 1], so you're not actually changing the texture coordinates (assuming you've enabled some sort of wrapping).
Try changing that increment (try .01f, or maybe something depending on the framerate) and see if it works. If not, then it may have something to do with the texture parameters you've got enabled.