Method and apparatus for rendering computer graphic images of translucent and opaque objects
View Patent ↗A method and an apparatus provided for rendering three-dimensional computer graphic images which include both translucent and opaque objects. A list of objects which may be visible in the images is determined and for each pixel in the list a determination is made as to whether or not the object in the list may be visible at that pixel. A data tag is stored for a transparent object determined to be visible at the pixel, and the data tag and object data are passed to a texturing and shading unit when the translucent object is determined to be overwriting the location in a tag buffer already occupied by another data tag.
1. A method for rendering 3-dimensional computer graphic images which include translucent and opaque objects, the method comprising the steps of:
subdividing a scene to be rendered into a plurality of rectangular subregions;
for each of the sub-regions, determining a list of objects which may be visible in the images;
for each pixel in each object in the list, determining whether or not the object in the list may be visible at that pixel;
storing a data tag for the translucent or opaque object determined to be visible at the pixel in a tag buffer; and
passing the data tag from the tag buffer and object data for the object to a texturing and shading unit in response to a determination that the translucent or opaque object is overwriting a location in the tag buffer already occupied by another data tag.
2. The method according to claim 1 further comprising the steps of:
clearing the data tags for the pixel from all the tag buffers when an opaque surface is determined to be visible at the pixel; and
storing a new data tag associated with the opaque surface.
3. The method according to claim 1 further comprising the steps of:
initially subdividing a scene to be rendered into a plurality of rectangular sub-regions; and
subsequently performing the method for each of the sub-regions.
4. The method according to claim 1 further comprising the steps of:
determining whether or not the object is a punch through object; and
performing a different process when the punch through object is detected.
5. The method according to claim 4 further comprising the steps of:
determining whether the punch through object is opaque;
clearing all the data tags from all the tag buffers for the pixels intersected by that object if an opaque object is detected; and
sending punch through object data to the texture and shading unit.
6. The method according to claim 4 further comprising the steps of:
determining whether the punch through object is translucent; and
passing all the data tags and the object data for the pixel to the texture and shading unit, including the object data for the translucent punch through object, if a translucent object is detected.
7. An apparatus for rendering 3-dimensional computer graphic images which include translucent and opaque objects, comprising:
means for subdividing a scene to be rendered into a plurality of rectangular sub-regions;
means for determining for each of the sub-regions a list of objects which may be visible in the images;
means for determining for each pixel in each object in the list whether or not the object in the list may be visible at that pixel;
a tag buffer for storing a data tag for the translucent or opaque object determined to be visible at the pixel; and
means for passing the data tag from the tag buffer and object data for the object to a texturing and shading unit in response to a determination that the translucent or opaque object is overwriting a location in the tag buffer already occupied by another data tag.
8. The apparatus according to claim 7 further comprising:
means for clearing all the data tags for the pixel from all the tag buffers when an opaque surface is determined to be visible at the pixel; and
means for storing in one of the tag buffers a new data tag associated with the opaque surface.
9. The apparatus according to claim 7 further comprising means for initially sub-dividing a scene to be rendered into a plurality of rectangular sub-regions and subsequently operating on each of the sub-regions.
10. The apparatus according to claim 7 further comprising:
means for determining whether or not the object is a punch through object; and
means for performing a different process when the punch through object is detected.
11. The apparatus according to claim 7 further comprising:
means for determining whether or not the punch through object is opaque;
means for clearing all the data tags from all the tag buffers for the pixels intercepted by the punch through object if it is opaque; and
means for sending opaque punch through object data to the texture and shading unit (TSU).
12. The apparatus according to claim 7 further comprising:
means for determining whether or not the punch through object is translucent; and
means for passing all the data tags and the object data for the pixel to the texture and shading unit if a translucent punch through object is detected, including object data for the translucent punch through object.