HDR
High Dynamic Range | wide dynamic rangeDescription of the color of the real physical quantities.
The familiar model description of the image is RGB, when all colors are presented in the form of the amount of the Basic colors: red, green, and blue, with different intensity in the form of a possible integer values from 0 to 255 for each, the encoded eight bits of the color. Attitude of the maximum intensity to the minimum available to display a particular model or device is called the dynamic range. Thus, the dynamic range of the RGB model is 256:1 or 100:1 cd/m2 (2). This model describe the color and intensity is generally accepted is called Low Dynamic Range (LDR).
The possible values of the LDR in all cases is not enough, a person is able to see a much greater range, especially at low light intensity, and the RGB model is too limited in such cases (yes, and when large �������������� too). The dynamic range of vision from 10-6 up to 108 cd/m2, that is, 100000000000000:1 (14 orders). At the same time, the entire range we see cannot, but the range, visible eye at a time, approximately equal 10000:1 (4). The vision adapts to the values from another part of the range of light conditions gradually, with the help of the so-called adaptation, you can easily describe the situation with the light off in the room at night - first the eyes see very little, but over time, adapt to changing light conditions and see the already much more. The same thing happens and when back to change the dark environment in the light.
So, the dynamic range of the RGB descriptions is not enough for the submission of images that people can see in reality, this model significantly reduces the possible values of light intensity at the top and bottom of the range. The most common example, driven in HDR, - the image of ������������ spaces with window to the bright street on a sunny day. With the RGB color model can be obtained or normal display that is located outside the window, or just the fact that inside the premises. Values greater than 100 cd/m 2 in the LDR is truncated, this is the reason that the 3D-rendering it is difficult to correctly display the bright light sources aimed directly in the camera.
The display device until that seriously cannot be improved, but the failure of the LDR in the calculations of makes sense. You can use the actual physical value of intensity and color (or linearly proportional), and on the monitor display maximum that it can. The essence of the submission of HDR in the use of intensity values and colors in real physical terms or linearly proportional to use integers and floating-point numbers with great accuracy (for example, 16 or 32 bits). This removes restrictions on the RGB, and the dynamic range images seriously increase. Then any HDR image can be displayed on any vehicle display (the same RGB monitor), with the highest quality possible for him with the help of special algorithms for tone mapping.
HDR rendering allows you to change the exposure after we ����������� image, gives an opportunity to simulate the effect of the adaptation of human vision (movement of bright open spaces in the dark spaces and vice versa), allows you to physically correct lighting, as well as a unified solution for the application of the postprocessing effects (glare, flares, bloom, motion blur). Algorithms of image processing, color correction, gamma correction, motion blur, bloom and other methods of qualitative processing performed in HDR view.
In the annexs 3D rendering Real Time Gaming, mostly) HDR rendering began to use relatively recently, because it requires computing and render target in the formats of floating point operations, which first became available only on the ���������� with support for DirectX 9. The usual route HDR rendering in games is as follows: the rendering of the scene in the buffer format of floating-point image postprocessing in the expanded color range (changing the contrast and brightness, color balance, the effects of glare and motion blur, lens flare and such), the application of tone mapping for the withdrawal of the final HDR images on the LDR screen. Sometimes the map used environment (environment maps) in the HDR formats, for the static reflections on objects, a very interesting application of HDR in the simulation of dynamic ����������� and reflections, this can also be used dynamic maps in formats with a floating point. To this add another �������� (light maps), pre-calculated and stored in the HDR format. Much of the above made, for example, in the Half-Life 2: Lost Coast.
HDR rendering is very useful for post-processing complex of higher quality, compared with conventional methods. The same bloom will look realistic in the calculations to HDR model of submission.
Unfortunately, in some cases, game developers can hide under the name of HDR filter simply bloom, calculated in the usual LDR range. Although a large part of that now make the games with HDR rendering, and there is a bloom of better quality, benefit from the HDR rendering is not limited to one these ������������, simply to make it easier.
