![]() "Images" presents the basic information about drawing, reading and copying pixel data."Bitmaps and Fonts" describes the commands for positioning and drawing bitmapped data.This chapter contains the following major sections: It also describes how to copy pixel data from one position to another, either from one buffer to another or within a single buffer. This chapter describes how to draw pixel data (bitmaps and images) from processor memory to the framebuffer and how to read pixel data from the framebuffer into processor memory. Also, bitmaps are like masks in that they're used to overlay another image, but image data simply overwrites or is blended with whatever data is in the framebuffer. One difference between them is that a bitmap consists of a single bit of information about each pixel, and image data typically includes several pieces of data per pixel (the complete red, green, blue, and alpha color components, for example). ![]() Image data, which might have been scanned in or calculatedīoth bitmaps and image data take the form of rectangular arrays of pixels.Bitmaps, typically used for characters in fonts.Two other important classes of data that can be rendered by OpenGL are So far, most of the discussion in this guide has concerned the rendering of geometric data - points, lines, and polygons. Control pixel-data formatting and perform other transformations as the data is moved to and from the framebuffer. ![]() Magnify or reduce an image as it's written to the framebuffer.Copy pixel data from one color buffer to another, or to another location in the same buffer.Read pixel data (bitmaps and images) from the framebuffer into processor memory and from memory into the framebuffer.What is the result ? Give 3 different ways to fix this.Drawing Pixels, Bitmaps, Fonts, and ImagesĪfter reading this chapter, you'll be able to do the following: Try not to generate mipmaps in The Compressonator.Do they give different result ? Different compression ratios ? Experiment with the various DDS formats.Change the code at the appropriate place to display the cube correctly. The DDS loader is implemented in the source code, but not the texture coordinate modification. ![]() In general, you should only use compressed textures, since they are smaller to store, almost instantaneous to load, and faster to use the main drawback it that you have to convert your images through The Compressonator (or any similar tool) Exercices You just learnt to create, load and use textures in OpenGL. You can do this whenever you want : in your export script, in your loader, in your shader… Conclusion So if you use compressed textures, you’ll have to use ( coord.u, 1.0-coord.v) to fetch the correct texel. Static const GLfloat g_uv_buffer_data = free ( buffer ) return textureID Inversing the UVsĭXT compression comes from the DirectX world, where the V texture coordinate is inversed compared to OpenGL. You'll learn shortly how to do this yourself. Here is the declaration of the loading function : So we’ll write a BMP file loader from scratch, so that you know how it works, and never use it again. But it’s very simple and can help you understand how things work under the hood. Knowing the BMP file format is not crucial : plenty of libraries can load BMP files for you. Notice how the texture is distorted on the triangle. These coordinates are used to access the texture, in the following way : This is done with UV coordinates.Įach vertex can have, on top of its position, a couple of floats, U and V. When texturing a mesh, you need a way to tell to OpenGL which part of the image has to be used for each triangle.
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