Left to right on the U axis and down to up on the V axis. OpenGL treats the values of the UV axes as going from The usual convention is to use U and V as the axis of the texture space where U corresponds to X in the 2D cartesian coordinate system and V corresponds to Y. The texture has a width of 320 and a height of 200 the texel location will be (160,20) (0.5 * 320 = 160 and 0.1 * 200 = 20). For example, if the texture coordinate is and This means that the textureĬoordinate is usually a fraction and by multiplying that fraction with the corresponding width/height of a texture we get the coordinate of the texel in the texture. Therefore, texture coordinates are specified in 'texture space' which is simply the normalized range.

Ideal scenario is to be able to change textures without changing texture coordinates. That would be too limiting because replacing a texture with one that has different width/height means that we will need to update the texture coordinates of all the vertices to match the new texture.

How do you specify the texture coordinates of a vertex? - No, it is not the coordinate of a texel inside Multiplying the width by height tells you the number of texels in the texture. A 2D texture has a width and height that can be any number OpenGL supports several types of textures such as 1D, 2D, 3D, cube, etc that can be used for different techniques. In the coming tutorials we will see that the texel can contain different types of data that can be used for multiple effects. The texel often contains a color which is used to paint the corresponding This action is known as 'sampling' and the result of sampling is a texel (a pixel in a texture). It interpolates the texture coordinates across the triangle face and in the fragment shader the developer maps these coordindates to the texture. To do this the developer supplies a set of coordinates known as 'texture coordinates' to each vertex. Will look real (if the texture appear to 'swim' across the triangle it will not). What the GPU needs to do is make the texture follow the movement of the vertices of the triangle so that it On the screen in numerous ways and look very different depending on its orientation to the camera. Since a triangle is scaled, rotated, translated and finally projected it can land Using the texture coordinates in order to get the pixel color.

To get texture mapping working you need to do three things: load a texture into OpenGL, supply texture coordinates with the vertices (to map the texture to them) and perform a sampling operation from the texture For example, compare the following images: The picture (a.k.a 'texture') can be anything but is often a pattern such as bricks, foliage, barren land, etc, that adds realism Texture mapping means applying any type of picture on one or more faces of a 3D model. Tutorial 16: Basic Texture Mapping Background

Opengl 4.4 texture units