Modeler

Images and MemoryMipmapping is a process where a series of images withprogressively lower resolutions are created from a base (fullresolution)image. Each pre-processed image is a power oftwo smaller than the previous level. As textures move fartheraway from the camera, they obviously must be scaled down.However, because the mipmaps are pre-processed and loadedinto memory, they can be used immediately for textures instead ofcontinually shrinking down the base image; this saves renderingtime, but requires more memory. Eight-bit greyscale and eight-bitindex-color images remain in eight-bit form internally. For colorimages, their mipmaps, however, are 24-bit since they mustinclude colors in between color palette entries.Chapter 1: LightWave 3D Getting Started 17High Dynamic Range Images (HDRI)In computer graphics, color is displayed as a triplet value: red,green and blue. These values typically range from 0 to 255.Those 256 steps of color represent eight bits and together allthree channels make up a 24-bit image. This means the maximumamount of color or luminance variation an image is allowed ismerely 256 steps.NOTE: See the discussion on radiosity foradditional information on high dynamic rangeimages.Greyscale images remain at eight-bit for mipmaps. Floating-pointimages use 96 bits per pixel and have 96-bit mipmaps.Here are some examples dealing with a 512 x 512 image invarious formats, and how much memory is used for the baseimage and the first couple mipmaps:512 x 512 eight-bit greyscale image:Base image 262,144 bytes (512 x 512 x 1)First mipmap 65,536 bytes (256 x 256 x 1)Second mipmap 16,384 bytes (128 x 128 x 1)Total 344,064 bytes512 x 512 eight-bit color-mapped image:Base image 262,144 bytes (512 x 512 x 1)First mipmap 196,608 bytes (256 x 256 x 3)Second mipmap 49,152 bytes (128 x 128 x 3)Total 507,904 bytes512 x 512 24-bit image:Base image 786,432 bytes (512 x 512 x 3)First mipmap 196,608 bytes (256 x 256 x 3)Second mipmap 49,152 bytes (128 x 128 x 3)Total 1,032,192 bytesIn the real world, the human eye can perceive a much higherrange of brightness and color values. Film can also react to amuch wider range. Video cameras, however, are limited to a fixedrange that fits closely to the same 256-step limit.When exposed to high dynamic range visuals, such as a sunset ora desert landscape, the lens of a camera will produce some levelof artifacting. Some of those artifacts can be seen as bloomingareas of brightness, color bleed, luminance spill, lens streaking,and many other visual cues that tell the viewer there is a verybright light source in the scene.These very bright surfaces can also contribute to the overalllighting of a scene. For example, sunlight streaming into a roomwill bounce off the floor and add a subtle illumination to the wallsand ceiling that would otherwise be left dark ( this bouncing oflight is known as radiosity). All of these effects can be seen inimages captured by devices that do not support high dynamicranges.Because computer graphics applications were designed tooutput to devices that would not understand pixel valuesabove RGB 255, 255, 255, most applications do not providefor any value to exceed these limits. LightWave, however,calculates all internal data without limits and with IEEE floatingpointaccuracy. This means that when LightWave points a light ata surface, while the final rendered pixel may reach only RGB 255,255, 255 for pure white, internally that pixel may have reached tentimes that amount. This may not seem significant at first glance —white is white after all — but, if we look at how LightWave utilisesthat data, it becomes very exciting.512 x 512 floating-point imageBase image 3,145,728 bytes (512 x 512 x 12)First mipmap 786,432 bytes (256 x 256 x 12)Second mipmap 196,608 bytes (128 x 128 x 12)Total 4,128,768 bytes