OpenGL – Build high performance graphics

Implementing the twirl filter using the fragment shader

We will use a simple image manipulation operator in the fragment shader by implementing the twirl filter on the GPU.

Getting ready

This recipe builds up on the image loading recipe from Chapter 1, Introduction to Modern OpenGL. The code for this recipe is contained in the Chapter3/TwirlFilter directory.

How to do it…

Let us get started with the recipe as follows:

1. Load the image as in the ImageLoader recipe from Chapter 1, Introduction to Modern OpenGL. Set the texture wrap mode to GL_CLAMP_TO_BORDER.

   int texture_width = 0, texture_height = 0, channels=0; GLubyte* pData = SOIL_load_image(filename.c_str(), &texture_width, &texture_height, &channels, SOIL_LOAD_AUTO); int i,j; for( j = 0; j*2 < texture_height; ...