# gdewan

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1. ## Reporting spam

Was reading the following article: http://www.gamedev.net/page/resources/_/technical/game-programming/not-all-is-fine-in-the-morrowind-universe-r4260 and noticed some spam that has been sitting in one of the comments for several weeks now.
2. ## Getting a deck of cards printed?

You might want to ask around here: http://www.bgdf.com/ Have no idea what their backlog might be but I suppose there is always Cartamundi (the people who print Magic: The Gathering, or at least used to). Don't know if they can do tarot type cards or not.
3. ## most fun 2D 1v1 multiplayer game?

Quote:Original post by owl Quote:Original post by Guthur Is that your game Owl? Looks good :) I wish. That's an old turn based strategy game I used to play when teenager. Advanced Civilization, which before being ported to the computer was a board game: http://www.boardgamegeek.com/boardgame/177
4. ## My sky is not blue

I have been trying to impliment a sky based on light scattering, using a variety of sources, including a paper by Hoffman & Preetham ( both what is posted on the ATI web site and in the book "Graphics Programming Methods". However I am getting sky colors that are effectively black. Using the original Hoffman & Preetham paper, it eventually comes down to the following formula (I am aware of the more advanced one in the book and intend to use it, but am trying to figure this problem out first): Lin(s, theta) = [ [ BetaR(theta) + BetaM(theta) ] / [ BetaR + BetaM ] ] * Esun[ 1 - e^-(BetaR + BetaS)s ] The part after Esun is going to produce a value between 0.0 and 1.0. The part before it is what is giving me troubles. It seems like it will be producing small numbers (below 0.1) for the most. As a result of this, my sky is too dark. Right now I am using an Esun of (1.0, 1.0, 1.0). If this is my problem, what would be a good value for Esun?
5. ## Realistic Skies

I just got started implimenting a realistic sky in my project using a paper called "Real Time Rendering of Atmospheric Scattering Effects for Flight Simulators" by Ralf Stokholm Neilsen. The pdf can be downloaded here: http://www.imm.dtu.dk/pubdb/views/edoc_download.php/2554/pdf/imm2554.pdf There is on place in the documentation (figure 2.2 on page 24) which shows BetaRayleigh as being [ 8 * x^3 * (n^2 - 1)^2 ] / [ 3 * N * Lambda^4 ]. n = refractivc index of air ( I used a value of 1.008 in my code ). N = molecular density of air ( I used a value of 2.687e25 in my code). Lambda = wavelength of light ( I use 650nm, 610nm, and 475nm in my code ). When I set up this arrary: static const double gRayleighScatteringTotal[3] = { ( 8.0 * gPi * gPi * gPi * ( 1.0008 * 1.0008 - 1.0 ) * ( 1.0008 * 1.0008 - 1.0 ) ) / ( 3.0 * 2.687e25 * 6.5e-7 * 6.5e-7 * 6.5e-7 * 6.5e-7 ), ( 8.0 * gPi * gPi * gPi * ( 1.0008 * 1.0008 - 1.0 ) * ( 1.0008 * 1.0008 - 1.0 ) ) / ( 3.0 * 2.687e25 * 6.1e-7 * 6.1e-7 * 6.1e-7 * 6.1e-7 ), ( 8.0 * gPi * gPi * gPi * ( 1.0008 * 1.0008 - 1.0 ) * ( 1.0008 * 1.0008 - 1.0 ) ) / ( 3.0 * 2.687e25 * 4.75e-7 * 4.75e-7 * 4.75e-7 * 4.75e-7 ) }; I get values of 4.4165646166911e-005, 5.6940158969630e-005, and 1.548687e-004 for red, green and blue. Is this reasonable? The reason I am asking is that later in the document, the author suggests (on page 64) that the blue component will be almost 10x greater than red component, but I only get a factor of 3.5, which in my mind is not almost 10.
6. ## DXT compression

Looks like it.
7. ## DXT compression

I misread the DXT5 format documentation. Looks like alpha is treated seperately (which makes a lot more sense) so I only need 3 dimensional linear fits. I also decided to use vertical offsets instead of perpendicular offsets as the perpendicular offsets seemed to involve a lot more work than they were worth.
8. ## DXT compression

I am working on my own DXT compressor, and at the heart of it I need to be able to perform a linear fit on a set of 4 dimensional points, preferably with perpendicular offsets. Right now I am taking the channel with the biggest delta as the independant variable and using each of the other channels as a dependant variable in a series of 3 linear fits using the formula indicated on this page: Least Squares Fitting Perpendicular Offsets What I am not sure about and what I would like to find out is exactly what it means if the denominator in step 15 equals 0. And if anyone knows of a description of a 4 dimension linear fit anywhere, I would like a link. edit: Can't seem to get the URL clickable. [edited by grhodes_at_work to make link clickable] [Edited by - grhodes_at_work on August 30, 2004 1:02:34 PM]