True-perspective texture/shading processor

In a computer image generator of the type wherein computations are performed in sequence by a plurality of groups including a first group which manages a visual data base and transfers data to an active environment storage of a second group, said first group determining the position of a viewpoint and any moving models in a common coordinate system and generating trigonometric coefficients required for perspective transformation, said second group reducing a three-dimensional description of the environment supplied by said first group to a two-dimensional description, making perspective transformation of data into coordinates of a view window and assigning a priority to each surface of the computed scene, and a third group which reduces the two-dimensional description generated by said second group to a scan line by generating edge data to locate where edges cross the scan line and responds to the assigned priorities to eliminate hidden surfaces and generates the video for display including edge smoothing, shading and texture effects, the improvement comprising texture/shading processing means which defines modulations globally over an entire simulated, visual environment, said texture/shading processing means comprising:

• face modulation processing means in said second group for computing data describing each one of a plurality of texture and shading models and data describing the plane of each one of a plurality of textured or shaded faces;
• texture/shading generator means in said third group responsive to initialization data from said first group and the data computed by said face modulation processing means for computing texture and shading modualtion signals based on a model using parallel planes defined in three-dimensional space to divide any number of faces into texture and shading stripes wherein said texture/shading generator means comprises:
• pattern memory means connected to said face modulation processing means for storing the data describing each texture and shading model;
• face memory means connected to said face modulation processing means for storing the data describing the plane of each textured or shaded face;
• edge memory means for storing edge data;
• data register means connected to said first group for storing a line and element number of a pixel at a relative line number and element number;
• edge crossing control means connected to said edge memory memory means and said data register means for computing a relative line number and element number;
• first distance calculator means connected to said face memory means and said edge crossing control means and responsive to data addressed by said edge memory means for computing the distance to each pixel group;
• first base number calculator means connected to said pattern memory means, said edge crossing control means and said first distance calculator means and responsive to data addressed by said face memory means for mapping each pixel group into texture stripe numbers;
• texture computer means connected to said first base number calculator means for storing texture modulating maps and computing blending and smoothing of the maps selected by the base number calculation;
• and
• first shading computer means connected to said first base number calculator means and said texture computer means for computing by linear interpolation the shading modulation based on the base number calculation and selecting shading, texture or no modulation to the video for display.