Re: spinning "E" demo questions, for ray casting & surface rendering
- Posted by achury May 18, 2009
- 1078 views
I'm not an expert, but I have studied a little this problems to make the galaxy emulator program.
My solution is to imagine the coordinate of the camera is the coordinate of the program user. When you see the program your eye is far from the screen, not in the screen itself. In my virtual world, between the observer/camera and the object to be observed there are a virtual screen, where each point is "retroprojected".
My program only show stars as points.
A simple example (by sure not the best approach), need a lot of geometric abstractions.
- You have a sequence with all the points on the "E"
- Create grups of points in order to define that define surface polygon. Descompose complex shapes triangles. Now you have a list of plain polygons defined by 3 points.
- Check that there is not two polygons that cross each other, may share a common limit but never cross.
- Determine the equation for the plain that contains each polygon z=ax+ by + c. Note, if you have descomposed complex shapes, you will have
- Create a function able to check if any line in the space z=dx+ey+f has an interception with a polygon (defined with the equation of the plane and the limitating points)
- Create a list of the points on the virtual screen, and check for each point, imagine a visual line between the observer/camera coordinates and such point on the virtual screen. Each visual line has an equation as previously descripted, you must to calculate the {d,e,f} coeficients for such line and using the function described up, check wich polygons are intercepted by such line. If more than one polygon is intercepted, calculate interception points and distance from observer in order to know wich is nearer to observer.
- Draw the selected polygon, and eliminate all their points on the visual screen from the list of points to be checked.
With this you get the polygon to be represented on each point of the screen. The color to paint the pixels depends on illumination... There begin the ray tracing, from ligth source to each point on your virtual objects.
