Textures

This article describes how images can be loaded from files and subsequently into textures for drawing. It will also show how to use multiple textures in a single drawing operation.

Loading an image

OOGL contains an Image container class that can load and save BMP, TGA, JPEG and PNG images. This can be done by specifying a path to a supported image file to the constructor.

GL::Image image( "/path/to/image.png" );

It is also possible to create an image yourself from a byte array or with SetPixel calls.

Creating a texture

Just like any other OpenGL object, textures have been wrapped into a class. A Texture can be created from scratch, but the constructor can also take a previously loaded or created Image instance.

GL::Texture tex( image );

There is an optional second parameter that can be used to specify the internal storage format of the texture, which defaults to RGBA.

Using a texture

To use a texture, first bind it to a texture unit by calling BindTexture.

gl.BindTexture( tex, 0 );

It can then be sampled with a sampler2D in a shader with the texture unit assigned to it.

Using multiple textures

Using multiple textures is as simple as using multiple texture units and multiple samplers bound to those units.

An example:

GL::Image im1( "/path/to/image1.png" );
GL::Image im2( "/path/to/image2.png" );
GL::Texture tex1( im1 );
GL::Texture tex2( im2 );

gl.BindTexture( tex1, 0 );
gl.BindTexture( tex2, 1 );

program.SetUniform( program.GetUniform( "t1" ), 0 );
program.SetUniform( program.GetUniform( "t2" ), 1 );

in vec2 Coords;
out vec4 outColor;
uniform sampler2D t1;
uniform sampler2D t2;
void main() {
	outColor = mix( texture2D( t1, Coords ), texture2D( t2, Coords ), 0.5 );
}

This example will blend two texture images. Note that it was previously not necessary to set the sampler unit because the value of the uniform defaults to 0 already.