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Rendering my (billiard) balls in a fragment shader

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Re: Rendering my (billiard) balls in a fragment shader

#71

Post by skywal_l »

ricardobayes wrote: post #70

Even after 10 years I still have anxiety looking at OpenGL code. I still don't understand why we needed to write ray-tracing during a BSc course starting from a blinking cursor. The professor tried to defend that at the time, but I firmly believe that it is the wrong curriculum for a 20 year old CS student. Computer graphics were and are niche programming, and should not be taught main-stream. Out of 100 graduates ma…

Because graphics is fun. It's a good way to engage with students. Beside, what's important is not the outcome but the journey. You learn to read documentation, to design, to debug and more importantly you learn to learn. Which is what higher education is about.

Re: Rendering my (billiard) balls in a fragment shader

#72

Post by jffhn »

zeristor wrote: post #41
xanthine wrote: post #13

I happened to notice that PI is #define'd to 3.1415926538, which isn't the correctly rounded off value of 3.14159265358... Seems like they missed a '5'.

Interesting point if it had been apparent it would have been an issue, at what point does a poor Pi become an issue? What would a Pi of 3.0 do?

The value was superior to mathematical Pi (as is best float approximation, but not best double approximation), such as having 2*PI normalized into [0,2*Pi] by standard trigonometric functions (which use accurate approximations of Pi) would not preserve it and yield a value close to 4.2e-10, which could cause suprises (for example if angular ranges are defined as (start,end) and not (start,span)).

Re: Rendering my (billiard) balls in a fragment shader

#73

Post by NavinF »

ricardobayes wrote: post #70

Even after 10 years I still have anxiety looking at OpenGL code. I still don't understand why we needed to write ray-tracing during a BSc course starting from a blinking cursor. The professor tried to defend that at the time, but I firmly believe that it is the wrong curriculum for a 20 year old CS student. Computer graphics were and are niche programming, and should not be taught main-stream. Out of 100 graduates ma…

inb4 you get 10 replies along the lines of "wow I wish my professors let me do something cool like ray-tracing. I spent 4 years implementing cache-inefficient data structures that nobody uses in an ancient version of some programming language that nobody uses in a crappy env doesn't even have a real debugger"

Not that I can relate. I dropped out of uni well before I encountered anything that would discourage me from going into software :)

Re: Rendering my (billiard) balls in a fragment shader

#74

Post by npteljes »

ricardobayes wrote: post #70

Even after 10 years I still have anxiety looking at OpenGL code. I still don't understand why we needed to write ray-tracing during a BSc course starting from a blinking cursor. The professor tried to defend that at the time, but I firmly believe that it is the wrong curriculum for a 20 year old CS student. Computer graphics were and are niche programming, and should not be taught main-stream. Out of 100 graduates ma…

Education is about exercising the mind. I don't think many play with inflated balls in their adulthood, yet it's very important to teach children hand-eye coordination, team play, and other concepts so that they become better functioning humans.

There are problems with the curriculum though, one of them that it plays catch-up with the state of the world. IT in particular moves very fast. Graphics programming is not one of these things however. For example, if you've done the courses, and experiences just how hard it is to crate anything in 3d, you can better appreciate the work that goes into modern 3d engines. Look at this beautiful breakdown of the inner workings of the GTA V engine:

http://www.adriancourreges.com/blog/2015/11/02/gta-v-graphic...

Re: Rendering my (billiard) balls in a fragment shader

#75

Post by underdeserver »

dang wrote: post #62
sysrpl wrote: post #7

Earlier quoted context omitted.

Fixed.

Not to pee on your party, but I wouldn't want to the users who click on that title expecting...something else, to be disappointed. Therefore I have made the minimum viable edit. (For anyone wondering: the submitted title was "Rendering my balls in a fragment shader" and the article title was changed from "Rendering pool balls" to that.)

I appreciate it. Happy that this isn't the place for this kind of humor.

Re: Rendering my (billiard) balls in a fragment shader

#78

Post by Jasper_ »

sysrpl wrote: post #2

Here is a summary I wrote on my attempt to render balls using only a fragment shader. I am pretty happy with the result, and I've included a breakdown of the creation process.

Nice work! My only recommendation is to add a pow(color, 1.0/2.2) or similar at the end, and then turn down your light brightness. Your light falloff has the distinctive look of gamma-space lighting makes it look dated and less realistic. Doing your lighting in linear space should help.

It might also be simpler to do your rotations without a matrix, for the learners ( just expand out the functions, e.g. https://github.com/magcius/sw3dv/blob/gh-pages/b_vert.glsl#L... )

Re: Rendering my (billiard) balls in a fragment shader

#79

Post by Jasper_ »

spuz wrote: post #30

I'm just getting my feet wet with shaders myself. Could this fragment shader be used in a "real" 3D game? At the moment, the sphere is orthographicly projected onto the screen so the sphere will always appear as a circle rather than an ellipse. How easy would it be to use this shader in place of a spherical mesh as you might find in a typical geometry based 3D render? I.e. could you use the same technique and render…

Think of it similar to an impostor: in world space, a sphere is always a sphere, and you should do all your lighting in world-space, so you don't need to account for the distortion. You do need to project into the camera's viewing, typically typically the projection matrix. But since a sphere under rotation has the same silhouette, you can also rotate the quad to view different parts of the sphere, and use a circle inside, though the rotation math would have to view a different part of the sphere. To integrate with other objects, you likely would turn on depth writing, and use gl_FragDepth to write the front depth to the buffer, and discard when outside of the silhouette.

Re: Rendering my (billiard) balls in a fragment shader

#80

Post by Jasper_ »

the__alchemist wrote: post #33

Good timing - I was procrastinating on HN instead of trying to fix my phucked-up phong; you've helped me do both.

The thing that got me, in a classic Phong, you have to test whether dot > 0.0, it really won't work outside of the front hemiphere. The clamp isn't enough.
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