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Texture appears white.

Started by Braden Apr 8, 2005 at 7:19 AM 11 replies 2.8k views

Original Post

Apr 8, 2005 at 7:19 AM

I am trying to load a texture directly into opengl using the DevIL/OpenIL library. The ilutGLLoatImage() returns successfully, but when it tries to draw the image on the screen it just looks white. Any ideas? Thanks, Braden



GLuint ui_textures[100];

void LoadUI_Image(unsigned long index, char *filename)
{
	GLuint tmp_texture;
	GLint x;
	GLint y;
	
	tmp_texture=ilutGLLoadImage(filename);
	glGenTextures(1,&ui_textures[index]);
	glBindTexture(GL_TEXTURE_RECTANGLE_ARB,ui_textures[index]);
	glGetTexLevelParameteriv(GL_TEXTURE_RECTANGLE_ARB,0,GL_TEXTURE_WIDTH,&x);
	glGetTexLevelParameteriv(GL_TEXTURE_RECTANGLE_ARB,0,GL_TEXTURE_HEIGHT,&y);
	glTexImage2D(GL_TEXTURE_RECTANGLE_ARB,0,3,x,y,0,GL_RGB,GL_UNSIGNED_BYTE,&tmp_texture);

	glDeleteTextures(1,&tmp_texture);
}


/* ...Inside of function trying to display the texture... */

glBindTexture(GL_TEXTURE_RECTANGLE_ARB,ui_textures[xml[needle].img_index]);
glGetTexLevelParameterfv(GL_TEXTURE_RECTANGLE_ARB,0,GL_TEXTURE_WIDTH,ℑ_size_x);
glGetTexLevelParameterfv(GL_TEXTURE_RECTANGLE_ARB,0,GL_TEXTURE_HEIGHT,ℑ_size_y);
glColor3f(1,1,1);
glEnable(GL_TEXTURE_RECTANGLE_ARB);
glBegin(GL_QUADS);
{
glTexCoord2f(0,0); glVertex2f(x+upperleftX,y+lowerrightY);
glTexCoord2f(0,image_size_y); glVertex2f(x+upperleftX,y+upperleftY);
glTexCoord2f(image_size_x,image_size_y); glVertex2f(x+lowerrightX,y+upperleftY);
glTexCoord2f(image_size_x,0); glVertex2f(x+lowerrightX,y+lowerrightY);
}
glEnd();
glDisable(GL_TEXTURE_RECTANGLE_ARB);

Basiror

Apr 8, 2005 at 7:37 AM

you need to create mipmaps

theres a function glubuildxyz maps search the glu specification on google

Braden

Apr 8, 2005 at 8:04 AM

My texture is not a power of 2 (hence the GL_TEXTURE_RECTANGLE_ARB), so I don't think I can do mipmaps.

darookie

Apr 8, 2005 at 8:05 AM

Seems as if your card doesn't support the extension.

_the_phantom_

Apr 8, 2005 at 8:29 AM

errm.. ilutGLLoadImage() loads an image directly into OpenGL and returns a GL handle to it, glTexImage2D() takes a pointer to the pixel data not an address of a varible with an OpenGL texture handle as its last parameter. You're probably lucky to get getting white and not some random pixels.

I wouldnt be overly shocked if ilutGLLoadImage is resizing your data to a power of two as well.

In short, this way wont work, find a way to load the raw pixel data.

Braden

Apr 8, 2005 at 8:47 AM

That is a very good point. How do I get a pointer to the pixel data? (using opengl functions).

jeroenb

Apr 8, 2005 at 8:51 AM

OpenGL isnt about loading textures etc into memory. If you want to get the bitmaps data you should make a file loader yourself and use glTexImage2D to insert that data in the texture (which is the required extensions are support, doesnt have to be a power of 2).

Braden

Apr 8, 2005 at 8:57 AM

Jeroenb,

Huh? That is not relevant to this topic.

I am wondering if there is an opengl function which can return a pointer to the pixel data or something of that nature.

_the_phantom_

Apr 8, 2005 at 9:08 AM

yeah, there is, glGetTexImage() is the function you are after.

However, i'm not convinced it will help as chances are that ilutGLLoadImage() call is going to resize the image to a power of two at best and at worse the texture upload will fail and you'll get nowt back.

As jeroenb says, you are better off loading it as raw pixel data and uploading it yourself than trying to bend IL and GL to some arcane purpose.

Braden

Apr 8, 2005 at 9:23 AM

hehehe. I like how you put that. Alright, I will re-think my design.

Hobitz

Apr 8, 2005 at 3:52 PM

Well I don't see a problem with devil.
You can load whatever you want and then get that pixel data from mem by
calling ilGetData();
Also you probably should need this:
ilGetInteger(IL_IMAGE_BYTES_PER_PIXEL);
ilGetInteger(IL_IMAGE_WIDTH);
ilGetInteger(IL_IMAGE_HEIGHT);
to make an actually ogl texture.
Hope it helps.

_the_phantom_

Apr 8, 2005 at 4:01 PM

as long as it doesnt do any resizing under the hood, then yes DevIL would be fine to loading the image data, however in this instance the useage of ilutGLLoadImage() which loads and uploads a texture to OGL probably does some resizing work under the hood

Hobitz

Apr 8, 2005 at 4:10 PM

Yes but why then not to use ilLoadImage() or even ilLoadL()
I think these are not resizing anything unless you resize texture by yourself.

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