The fragment shader above could be written as: #version 330 The result f could then be used as a parameter in the mix function to select the final color. None of the above are what we are looking for, but when we combine them as follows, we get exactly what we want:į = smoothstep(0.4, 0.5, t.s) - smoothstep(0.9, 1.0, t.s) Here are two examples of the resulting curves calling this function with different parameters: the threshold constant defines the with of the linesīetween edge0 and edge1, this function performs Hermite interpolation (smooth cubic curve) between 0 and 1. Vec2 t = texCoordV * multiplicationFactor multiplicationFactor scales the number of stripes Varying this value and the threshold alters the number of grid cells and their width, respectively. Below we set the stripe multiplication factor to 8. The vertex shader is the same as above, only the fragment shader needs to be rewritten. This last value, 0.1, controls the width of the lines drawn. The fragment shader then selects only those pixels that have one of the texture coordinates with a fractional value below 0.1, painting these with blue color. The density of the grid is defined by a multiplication factor applied to the texture coordinates. To achieve the above we are only painting certain pixels (in blue) and discarding the remaining pixels with the GLSL keyword discard. For instance, assume that we want to obtain a grid effect as shown in the image below: Texture coordinates can also be used for some interesting effects. These shaders can be useful for debugging when texturing with an image provides unexpected results. Red will be used for the s coordinate, and green for the t coordinate. For instance, the figure below shows a plane, an elephant, and the teapot, with their texture coordinates. The output of these shaders displays texture coordinates as colors, showing how the texture mapping is defined in a model. The code below illustrates the process described above: this variable will be received as input in the fragment shader, where we can use it for the purpose of our application. In the vertex shader we shall receive the texture coordinates as inputs, and commonly we simply copy them to an output variable. we need to add a buffer with the texture coordinates to the vertex array object that contains all the other models attributes (see this section for more details on attributes). Hence in the application we need to treat them as such, i.e. Texture coordinates are just another vertex attribute, much like normals. The first step is making the textures coordinates available to our shaders. Here we will see a couple examples of how texture coordinates can be used on their own. Texture coordinates per se can be used to color a model. However texture coordinates are not restricted to perform this mapping. Texture coordinates are commonly used to define how an image maps to a surface.
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