Volume Rendering and Ray Casting

Volume Rendering and Ray Casting

Post by Cristian Faraoni mat.4 » Tue, 18 Mar 1997 04:00:00



Excuse me for my poor english.
I am an Italian student in computer science of the University of Bologna.
I am developing the thesis on an algorithm of volume rendering on parallel machine.
I have read several articles on the matter (Levoy, Heidelberger, etc.) but I still have many doubts about it.

1) how should I take care of the voxels and their correlated data (gradient, opacity, fonts of light, etc.) with
regards to the trasformations of view (perspective and orthographic). Since I have to elaborate too many voxels
and related data, when i calculate the trasformation of view (using the matrix of  trasformation) and the final
image (i use the ray casting) i should trasform all the coordinates of the voxels,
gradient, fonts of light etc. in the coordinates view (as the algorithms of ray tracing say).
I'd like to know, if it's right to calculate the origin of the rays and their directions in the
coordinates view and trasform them in the coordinates world, without modify the coordinates of the voxels.

2) I'd like to have some info about the C data structures  about algorithms of ray casting and what
files should be created from the given data sets (MRI and TAC).

3) In an article of Robert A. Drebin: "Volumetric Rendering of Computed Tomography Data: Principles and
Techniques" he speaks about "bicubic interpolation", what is it?

Thanks in advance.
Please help me...SIGH!

FARAONI CRISTIAN
Forli' (ITALY)


 
 
 

Volume Rendering and Ray Casting

Post by Dirk Bart » Thu, 20 Mar 1997 04:00:00



> 1) how should I take care of the voxels and their correlated data (gradient, opacity, fonts of light, etc.) with
> regards to the trasformations of view (perspective and orthographic). Since I have to elaborate too many voxels
> and related data, when i calculate the trasformation of view (using the matrix of  trasformation) and the final
> image (i use the ray casting) i should trasform all the coordinates of the voxels,
> gradient, fonts of light etc. in the coordinates view (as the algorithms of ray tracing say).
> I'd like to know, if it's right to calculate the origin of the rays and their directions in the
> coordinates view and trasform them in the coordinates world, without modify the coordinates of the voxels.

I'm not sure if I understand you correctly. Calculating the positions
of the samples of the ray is done using the viewing transformation.

Quote:> 2) I'd like to have some info about the C data structures  about algorithms of ray casting and what
> files should be created from the given data sets (MRI and TAC).

> 3) In an article of Robert A. Drebin: "Volumetric Rendering of Computed Tomography Data: Principles and
> Techniques" he speaks about "bicubic interpolation", what is it?

Bicubic is the same as bilinear, just with a cubic interpolition
(using a cubic polynom instead of a linear). The linear interpolation
interpolates between two points. The bilinear interpolation interpolates
between four points.

Hope that helps,

Dirk

--

==== 8< ======= 8< ======= 8< ======= 8< ======= 8< ======= 8< ====
Dirk       Phone:  +49-9131/85-9924

           WWW:    http://www9.informatik.uni-erlangen.de/~dkbartz

 
 
 

1. Volume Rendering and Ray Casting

Excuse me for my poor english.
I am an Italian student in computer science of the University of Bologna.
I am developing the thesis on an algorithm of volume rendering on parallel machine.
I have read several articles on the matter (Levoy, Heidelberger, etc.) but I still have many doubts about it.

1) how should I take care of the voxels and their correlated data (gradient, opacity, fonts of light, etc.) with
regards to the trasformations of view (perspective and orthographic). Since I have to elaborate too many voxels
and related data, when i calculate the trasformation of view (using the matrix of  trasformation) and the final
image (i use the ray casting) i should trasform all the coordinates of the voxels,
gradient, fonts of light etc. in the coordinates view (as the algorithms of ray tracing say).
I'd like to know, if it's right to calculate the origin of the rays and their directions in the
coordinates view and trasform them in the coordinates world, without modify the coordinates of the voxels.

2) I'd like to have some info about the C data structures  about algorithms of ray casting and what
files should be created from the given data sets (MRI and TAC).

3) In an article of Robert A. Drebin: "Volumetric Rendering of Computed Tomography Data: Principles and
Techniques" he speaks about "bicubic interpolation", what is it?

Thanks in advance.
Please help me...SIGH!

FARAONI CRISTIAN
Forli' (ITALY)


2. Corel 5 & Textures

3. Volume Rendering with POV-Ray

4. Mapping Modes

5. POV-Ray and volume ray tracing?

6. HELP: Selecting Framebuffers on SGI machines

7. Ray casting.

8. Casting but not receiving shadows in POV-Ray 3.0 for windows

9. ray casting

10. Ray casting problem: Gap on block

11. Ray casting problem: walls with block borders sticking out

12. squashed sphere in ray casting