Global illumnation and radiosity~

[actarus1]

Hi everyone~
Does global illumination and radiosity do the same things behind? Because I seen the screenshot of using radiosity (e.g lightwave) and GI (e.g. softimage) seems have the same effect, which is simulate the natural light around the world in the scene. So, can I say that "The function of radiosity in lightwave, is equal to golbal illumination in softimage, but just changed the function name"? Please correct my idea if I am wrong~
And also, I like to give rank to the 3d software, so I always ask the lecturer and classmate that "softimage and MAYA, which is the no.1 in the world?" but my lecturere told me "Don't have this idea, don't try to give rank to any 3d software in your mind, only the software is good to use, then it's good" can anyone give comment to me about this idea?

[devdoka]

Off the top of my head I don't remember the differences, but Global Illumination and Radiosity are not the same. They attempt to create the same end result, but the methods are different.

Matt

---

Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com

[colinsenner]

In reply to:

Hy solution,

GI and Radiosity uses different rendering algorithms.
I have to say that i haven't a real knowledge about the mathematical background or theories behind this rendering techniques, but as i know radiosity (with which i get first contacted with lightwave) is based of energy calculation from any surface in the scene (based on energy value of any object/triangle), so when only the camera view is changing nothing have to recalculate, because scenes energy 'state' doesnt change. (this is similar to softs 'use photon map' option what also prevent from recalculating the photon emmission).
On the other hand GI uses photon rays, emitted from a light source bouncing through the scene.
Radiosity consumes more memory but gives a better result.
i.e. softer edges of indirect illumination. Im not sure but I think Radiosity cant compute caustics...

My comment to the 'software ranking' thing, is simple:

Its not the software but the operator, the animator, the experience. Its a strange envolvement that software features, plugins and all that get overrated. Becomes more than they just are - tools for the operators. As long as Presentations and roadshows are on a level of an washing powder advertisment, students get impressed by flashy particle explosions and these 'bombastic effects with just one mouseclick' A 'good' software means a good artist and a bad software means a weak artist? Yeahh, right...
Like your lecturer says, you use! the software - the better you use it, the better the results are ... and your skills, of course.

sven

[pomme]

Gl is calculate the light from each triangle itself as a light transmitter. Therefore, render in GI, no light source is needed.

However, in radiosity, each triangle is acting as a light transmitter and reciver. Scene must be lit by a light source. And the light will goes to the triangle (recive) and bounce Off from the same triangle (triansmit). Same as the other triangle, recive more than 1 light source since the other triangles are transmitting light. That light logic simulates the real world around us. However, radiosity render time is double of GI. However, GI gives us the simular effect. I suggest using GI. Softimage also has GI, so you may want to have a try.

For the compare question. I am totally agree with sven. There have only good artist in the world. A good application experty isn't do anything. Keep in mind that 3D application is a tool or medium for artist to make their works achive. But still you can compare the two applications such as, which is more powerful, which one is more easy to use. It depence, I would say, softimage does the best on animation. The world most simple and user friendly interface for animation. But for modeling, Maya stills in the lead. XSI well, has improve but I still think that Maya is easier on modeling.

I think, i 've answer your question
HapZungLam

[actarus1]

Really thanks alots all of your experiences~ thank you very much~
then, I've some questions, is it softimage can only do global illumination but can't do radiosity? because I can't see any option to use radiosity in softimage.... and also, does there any other software also have global illumination function?
and, how about these 2 features in Maya, does maya have global illumination and radiosity?

[pomme]

Yes, Softimage does have radiosity. But, i've try to use it. It just gave me headaches. I know that Maya doesn't have any complicate render. Maya's render is the most funny joke in 3D world. However, with a addon of render man. Maya will be able to do radiosity and GI.

HapZungLam

[actarus1]

In reply to:
Yes, Softimage does have radiosity. But, i've try to use it. It just gave me headaches. I know that Maya doesn't have any complicate render. Maya's render is the most funny joke in 3D world. However, with a addon of render man. Maya will be able to do radiosity and GI.

HapZungLam

hi hapzunglam,
how to activate the radiosity function in softimage?

[slepa]

" Yes, Softimage does have radiosity."
This is technically true, but misleading. Radiosity is a subset of GI.

"But, i've try to use it. It just gave me headaches. "
Try harder then. It's quite easy, even fun.

"I know that Maya doesn't have any complicate render. Maya's render is the most funny joke in 3D world."
Agreed.

"However, with a addon of render man. Maya will be able to do radiosity and GI."
Uh, no. PRMan DOES NOT raytrace. Period.

[pomme]

Setup Radiosity. This is my way of doing it, I don't find that good, if anyone has anyother way of doing it. Please tell me.

At your scene, get a large scaled grid. That simulate the ground. Get a poly sphere-> raycast the lower half of the sphere-> poly mode -> delete selected. it ends up with a holo half sphere-> effect-> invert(make normal facing in-> scale it so that it has the simular size as the grid. This simulate the sky. Make sure that your camara is inside the sphere and the grid, and all of your scene element is inside the sphere. Get a infinite light-> ratrace shadow. You may want to add one more light to soften the other side of your side. That's totally up to you. Go to light ->photondirector -> rendersetup -> check finall gathering -> give a value of 600 -> at this point, leave the max and min thing -> click OK -> OK again. go Render -> make sure that it is MR -> render sequence. You should get somehting very bright. Go back and adjust the colour of the light. And if posible, give the sphere and the grid a material. Usually the sphere is white, and the grid can be any colour you want. Re-render until you feel comforable with the colour and seting. You knowtice that you may get some squares on your rendered pictures. That deels with the min and max in final gathering. I usually put value under 5 in both (Max > min).

What i am suffering with radiosity is that although I put the min and max value very small. I still have some black thing on surface. I never know how to fix those. There has another guy posted the same question couple weeks ago. But there has no reply. So that i don't know how to fix it. That drives me nuts. Anyways, you give it a try. You still have fun. Good luck

[hypersim]

Just to complicate things further, what is the difference between GI and Final Gathering in Softimage??? It seems that you can yield good results from having either both of them on or just one, but they produce slightly different results.