using multiple textures

Submitted by shagendo on March 17, 2008 - 4:20pm.

General Discussion

Hi,

I'm trying to display several quads with textures, but so far i'm not getting anywhere.
If I only use one texture, it displays perfectly.
But when I try to use more than one, the other textures show up as white. The bitmaps used are 128x128 pixels.
I'm using VS2005 sp1 and have tried tao 2.0 and the latest beta (2.1.0.12/1.0.0.4).

This is the code I use for loading the textures:
texture1 = new int[] { 0 };


//generate holders for 5 textures

Gl.glGenTextures(1, texture1);
Gl.glBindTexture(Gl.GL_TEXTURE_2D, texture1[0]);
bitmap1 = new Bitmap("c:\\dv_ecg.bmp");

data1 = bitmap1.LockBits(new Rectangle(0, 0, bitmap1.Width, bitmap1.Height),

ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
Gl.glTexImage2D(Gl.GL_TEXTURE_2D, 0, Gl.GL_RGB, data1.Width, data1.Height, 0,

Gl.GL_BGR, Gl.GL_UNSIGNED_BYTE, data1.Scan0);

bitmap1.UnlockBits(data1);

The code i use for rendering the textures:
Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MAG_FILTER, Gl.GL_NEAREST);// LINEAR); Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MIN_FILTER, Gl.GL_NEAREST); Gl.glEnable(Gl.GL_TEXTURE_2D);


Gl.glBindTexture(Gl.GL_TEXTURE_2D, texture1[0]);

Gl.glBegin(Gl.GL_QUADS);
// Display a quad texture to the screen

Gl.glColor3f(1f, 1f, 1f);

// Display the top left vertice

Gl.glTexCoord2f(0.0f, 0.0f);

Gl.glVertex3f(startX, startY, 0.0f);
// Display the bottom left vertice

Gl.glTexCoord2f(0.0f, 1.0f);

Gl.glVertex3f(startX, endY, 0.0f);
// Display the bottom right vertice

Gl.glTexCoord2f(1.0f, 1.0f);

Gl.glVertex3f(endX, endY, 0.0f);
// Display the top right vertice

Gl.glTexCoord2f(1.0f, 0.0f);

Gl.glVertex3f(endX, startY, 0.0f);

Gl.glEnd();

When using the above code for one texture, it's ok, when using multiple textures only the last one displays ok, the others remain white.
I've tried using a single array (textures[]) to store the textures, or a seperate array (texture1[], texture2[], etc). No luck... is there anyone who can help out?

Kind regards,
Sander

texture1 = new int[] { 0

Submitted by SeaEagle1 on March 17, 2008 - 5:28pm.

texture1 = new int[] { 0 }; //generate holders for 5 textures Gl.glGenTextures(1, texture1);

generates 1 texture, did you try

texture1 = new int[5]; //generate holders for 5 textures Gl.glGenTextures(5, texture1);

and then load/render the textures using texture1[0] to texture1[4]?

I did, but it yields exactly

Submitted by shagendo on March 18, 2008 - 7:34am.

I did, but it yields exactly the same result.
I've tried the array approach, I've tried separate variables for bitmap en textures, everything I can think of. There must be something logically wrong with the way I set up and render the textures, I suppose...
Does anyone have a clue?

How are you rendering them?

Submitted by SeaEagle1 on March 18, 2008 - 12:04pm.

How are you rendering them? All at once or one by one?

I repeat the code between

Submitted by shagendo on March 18, 2008 - 12:30pm.

I repeat the code between "#region texture 1" and "#endregion" for each texture (using texture1[], texture2[] etc, or even texture1[0], texture1[1] etc), then end with Gl.glDisable(Gl.GL_TEXTURE_2D);.

I see no #regions but your

Submitted by SeaEagle1 on March 18, 2008 - 12:46pm.

I see no #regions but your loop should start with the 2nd glBindTexture and end with glEnd. And you should do the same when loading ofcourse, starting with the 1st glBindTexture, ending with UnlockBits.

I suppose that's exactly

Submitted by shagendo on March 18, 2008 - 1:43pm.

I suppose that's exactly what I do...
For completeness, here's my render code (and the missing regions)
#region texture 1 Gl.glBindTexture(Gl.GL_TEXTURE_2D, texture1[0]); Gl.glBegin(Gl.GL_QUADS);


Gl.glColor3f(1f, 1f, 1f);
// Display the top left vertice

Gl.glTexCoord2f(0.0f, 0.0f);

Gl.glVertex3f(startX, startY, 0.0f);
// Display the bottom left vertice

Gl.glTexCoord2f(0.0f, 1.0f);

Gl.glVertex3f(startX, endY, 0.0f);
// Display the bottom right vertice

Gl.glTexCoord2f(1.0f, 1.0f);

Gl.glVertex3f(endX, endY, 0.0f);
// Display the top right vertice

Gl.glTexCoord2f(1.0f, 0.0f);

Gl.glVertex3f(endX, startY, 0.0f);

Gl.glEnd(); #endregion

Ok, I found the

Submitted by shagendo on March 20, 2008 - 7:45am.

Ok,

I found the solution:

Before every Gl.glTexImage2D() call, the following call should be made
Gl.glTexParameteri(Gl.GL_TEXTURE_2D, Gl.GL_TEXTURE_MIN_FILTER, Gl.GL_NEAREST);
If this call is missing, the textures show up as white.
Is this behavior explainable?

Regards,
Sander

If you change Gl.GL_NEAREST

Submitted by StApostol on March 20, 2008 - 4:09pm.

If you change Gl.GL_NEAREST with Gl.GL_LINEAR, does it still work? What about Gl.GL_LINEAR_MIPMAP_NEAREST?

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OpenTK

Hi StApostol, Thanks for

Submitted by shagendo on March 21, 2008 - 9:22am.

Hi StApostol,

Thanks for your reply.
I will be back @ work next tuesday, and I'll report on your questions then.

Regards,
Sander

I've tried the

Submitted by shagendo on March 25, 2008 - 7:53am.

I've tried the following:

GL_LINEAR - works like GL_NEAREST, but still need to issue this call before every glTexImage2D call
GL_LINEAR_MIPMAP_NEAREST - doesn't work, all textures show up as white

Regard,
Sander

GL_LINEAR - works like

Submitted by StApostol on March 25, 2008 - 10:54am.

GL_LINEAR - works like GL_NEAREST, but still need to issue this call before every glTexImage2D call
That's correct. You need to set texture parameters for each texture (at some point after glGenTextures).

GL_LINEAR_MIPMAP_NEAREST - doesn't work, all textures show up as white
This means you are not building mipmaps for the texture, i.e. you only upload a texture for level-0 (check the 'level' parameter in glTexImage2D).

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OpenTK