GRADIENT FREE SHADING FOR VOLUME RENDERING USING SHADOW INFORMATION

• US 20070002047A1
• Filed: 05/18/2006
• Published: 01/04/2007
• Est. Priority Date: 06/03/2005
• Status: Active Grant

• Current Assignee: Siemens Healthineers AG (Siemens AG)
• Original Assignee: Siemens Corporate Research Incorporated (Siemens AG)
• Inventors: Engel, Klaus, Desgranges, Philippe
• Granted Patent: US 8,884,959 B2
• Time in Patent Office: Days
• US Class Current: 345/426
• CPC Class Codes: G06T 15/60 Shadow generation

Abstract

Disclosed is a method and apparatus for computing the shading of a volume. A slice of the volume is rendered along a half-angle direction that is between a light direction and a view direction. A slice of the volume is then rendered along a light direction to assimilate shadow information of the slice in a shadow buffer. The shadow buffer is bled orthogonal to the light direction to shade the slice.

Claims

1. A method for computing shading of a volume comprising:

rendering a slice of said volume along a half-angle direction that is between a light direction and a view direction;

rendering a slice of said volume along a light direction to assimilate shadow information of said slice in a shadow buffer; and

bleeding said shadow buffer orthogonal to said light direction to shade said slice.

2. The method of claim 1 wherein said bleeding said shadow buffer comprises scaling said shadow buffer.

3. The method of claim 1 wherein said bleeding said shadow buffer comprises dilating said shadow buffer.

4. The method of claim 1 wherein said bleeding said shadow buffer comprises bleeding with a central offset.

5. The method of claim 4 wherein bleeding with a central offset comprises, for a first pixel of the shadow buffer, locating a second pixel that is closer to a center point of said shadow buffer at a given distance from said first pixel.

6. The method of claim 5 further comprising performing a correction if said second pixel is too close to said center point.

7. The method of claim 6 further comprising replacing said first pixel with said second pixel.

8. The method of claim 1 comprising, after said bleeding, rendering said slice using said shadow map.

9. The method of claim 8 wherein said rendering said slice using said shadow map comprises at least one of rendering without gradients, rendering with selective specular fighting, and rendering with selective Blinn/Phong.

10. The method of claim 9 wherein said rendering said slice using said shadow map further comprises computing diffuse lighting with said shadow map.

11. An apparatus for computing shading of a volume comprising:

means for rendering a slice of said volume along a half-angle direction that is between a light direction and a view direction;

means for rendering a slice of said volume along a light direction to assimilate shadow information of said slice in a shadow buffer; and

means for bleeding said shadow buffer orthogonal to said light direction to shade said slice.

12. The apparatus of claim 11 wherein said means for bleeding said shadow buffer comprises means for scaling said shadow buffer.

13. The apparatus of claim 11 wherein said means for bleeding said shadow buffer comprises means for dilating said shadow buffer.

14. The apparatus of claim 11 wherein said means for bleeding said shadow buffer comprises means for bleeding with a central offset.

15. The apparatus of claim 14 wherein means for bleeding with a central offset comprises, for a first pixel of the shadow buffer, means for locating a second pixel that is closer to a center point of said shadow buffer at a given distance from said first pixel.

16. The apparatus of claim 15 further comprising means for performing a correction if said second pixel is too close to said center point.

17. The apparatus of claim 16 further comprising means for replacing said first pixel with said second pixel.

18. The apparatus of claim 11 comprising means for rendering said slice using said shadow map.

19. The apparatus of claim 18 wherein said means for rendering said slice using said shadow map further comprises means for computing diffuse lighting with said shadow map.