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joekarl

Member Since 11 Aug 2010
Offline Last Active Oct 12 2012 04:09 PM

Topics I've Started

Interpolating color across a polygon

12 October 2012 - 01:39 PM

I'm working on a software rasterizer just for grins and I'm to the point where I want to implement smoothing between different colors at vertices across a polygon.

From what I've read, it consists of calculating a scan line, calculating the colors at the ends of the scan line, and then linearly interpolating across that scan line to get the color at a single point.

My question is how to calculate the color at the end of the scan line for polygons with 4+ points. 3 points is pretty straight forward (though I haven't actually done the calculations yet), but 4 is a bit harder to wrap my head around.

Anyone have any good resources (or code) to get me started?

Handling polygons in multiple nodes of an Octree

18 January 2012 - 01:25 PM

I'm building a 3d software renderer for grins to learn the math and rendering concepts. I've implemented the basic drawing of polygons with some basic optimizations like back face culling and frustrum culling. Its going pretty well for it being java and all (15k polygons at 30fps at 1900x1080) but I want to implement an Octree to reduce the amount of overdraw happening and correctly sort the polygons for drawing without using a z-buffer for the entire screen.

I get the basic ideas of how to partition the world and how to traverse the tree from front to back to order the polygons correctly, but I'm a bit confused on how to handle polygons that are in more than one node of the Octree.

Some example cases I'm concerned about are:
  • A floor of 2 big polygons that intersect all of the nodes at the bottom of the Octree
  • A polygon that extends across a node boundary
I figure I should split the polygon at the node boundaries, but then do I need to check on each frame for objects that have moved in the world that need recalculation in the Octree.

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