Topics

1

Projects / mode 7 in OpenGL

« on: April 29, 2019 »

Recreated the SNES's mode 7 in OpenGL. just thought id share as there are some good people on these forums and might help encourage others.

it still needs work. for example to do rotation i rotate the texture UV co-ords. not the texture its self. which creates the effect of having the whole screen rotate rather than just the texture when viewed with the scanline scaling enabled. Its my first OpenGL program.

I also implemented it on the CPU in C/SDL and was dropping many frames, doing everything per pixel with for loops for anything high res. Or even low res for that matter.

https://github.com/flightcrank/java-opengl-mode-7-demo

2

Coding tutorials / metaball video tutorial by daniel shiffman (in processing)

« on: July 19, 2016 »

Hey guys heres a cool metaball tutorial by daniel shiffman who also has other cool tutorials relevant to demoscene coding.
As metaballs are popular in the demoscene i thought id post this one. i hope it helps out people (like me) who has trouble
in written tutorials when they throw to much math at you with not enough explanation behind it.

https://www.youtube.com/watch?v=ccYLb7cLB1I

3

General coding questions / Create a radial gradient

« on: August 07, 2013 »

Hi all.

I am having a little trouble creating a radial gradient. Also I can not find any documentation on creating them programaticly.

Here is where I'm at so far:

Assume I want to make a radial gradient fill a small 16px width by 16px height rectangle/square. I take the center pixel (x =8 , y = and I calculate the distance each pixel in the rectangle is from that center pixel using Pythagoras theorem. I'm left with a table of values that look like this

Code: [Select]

11.31  10.63  10.00   9.43   8.94   8.54   8.25   8.06   8.00   8.06   8.25   8.54   8.94   9.43  10.00  10.63
 10.63   9.90   9.22   8.60   8.06   7.62   7.28   7.07   7.00   7.07   7.28   7.62   8.06   8.60   9.22   9.90
 10.00   9.22   8.49   7.81   7.21   6.71   6.32   6.08   6.00   6.08   6.32   6.71   7.21   7.81   8.49   9.22
  9.43   8.60   7.81   7.07   6.40   5.83   5.39   5.10   5.00   5.10   5.39   5.83   6.40   7.07   7.81   8.60
  8.94   8.06   7.21   6.40   5.66   5.00   4.47   4.12   4.00   4.12   4.47   5.00   5.66   6.40   7.21   8.06
  8.54   7.62   6.71   5.83   5.00   4.24   3.61   3.16   3.00   3.16   3.61   4.24   5.00   5.83   6.71   7.62
  8.25   7.28   6.32   5.39   4.47   3.61   2.83   2.24   2.00   2.24   2.83   3.61   4.47   5.39   6.32   7.28
  8.06   7.07   6.08   5.10   4.12   3.16   2.24   1.41   1.00   1.41   2.24   3.16   4.12   5.10   6.08   7.07
  8.00   7.00   6.00   5.00   4.00   3.00   2.00   1.00   0.00   1.00   2.00   3.00   4.00   5.00   6.00   7.00
  8.06   7.07   6.08   5.10   4.12   3.16   2.24   1.41   1.00   1.41   2.24   3.16   4.12   5.10   6.08   7.07
  8.25   7.28   6.32   5.39   4.47   3.61   2.83   2.24   2.00   2.24   2.83   3.61   4.47   5.39   6.32   7.28
  8.54   7.62   6.71   5.83   5.00   4.24   3.61   3.16   3.00   3.16   3.61   4.24   5.00   5.83   6.71   7.62
  8.94   8.06   7.21   6.40   5.66   5.00   4.47   4.12   4.00   4.12   4.47   5.00   5.66   6.40   7.21   8.06
  9.43   8.60   7.81   7.07   6.40   5.83   5.39   5.10   5.00   5.10   5.39   5.83   6.40   7.07   7.81   8.60
 10.00   9.22   8.49   7.81   7.21   6.71   6.32   6.08   6.00   6.08   6.32   6.71   7.21   7.81   8.49   9.22
 10.63   9.90   9.22   8.60   8.06   7.62   7.28   7.07   7.00   7.07   7.28   7.62   8.06   8.60   9.22   9.90

Now am I on the right track here ? it seems like I am and that it makes sense to do it this way.. but now I'm stuck and cant actually draw the gradient.

so far I have tried to take the inverse of each number by dividing 1 by each number which give me this... each number is between 0 and 1.0

Code: [Select]

0.09   0.09   0.10   0.11   0.11   0.12   0.12   0.12   0.12   0.12   0.12   0.12   0.11   0.11   0.10   0.09
  0.09   0.10   0.11   0.12   0.12   0.13   0.14   0.14   0.14   0.14   0.14   0.13   0.12   0.12   0.11   0.10
  0.10   0.11   0.12   0.13   0.14   0.15   0.16   0.16   0.17   0.16   0.16   0.15   0.14   0.13   0.12   0.11
  0.11   0.12   0.13   0.14   0.16   0.17   0.19   0.20   0.20   0.20   0.19   0.17   0.16   0.14   0.13   0.12
  0.11   0.12   0.14   0.16   0.18   0.20   0.22   0.24   0.25   0.24   0.22   0.20   0.18   0.16   0.14   0.12
  0.12   0.13   0.15   0.17   0.20   0.24   0.28   0.32   0.33   0.32   0.28   0.24   0.20   0.17   0.15   0.13
  0.12   0.14   0.16   0.19   0.22   0.28   0.35   0.45   0.50   0.45   0.35   0.28   0.22   0.19   0.16   0.14
  0.12   0.14   0.16   0.20   0.24   0.32   0.45   0.71   1.00   0.71   0.45   0.32   0.24   0.20   0.16   0.14
  0.12   0.14   0.17   0.20   0.25   0.33   0.50   1.00    inf   1.00   0.50   0.33   0.25   0.20   0.17   0.14
  0.12   0.14   0.16   0.20   0.24   0.32   0.45   0.71   1.00   0.71   0.45   0.32   0.24   0.20   0.16   0.14
  0.12   0.14   0.16   0.19   0.22   0.28   0.35   0.45   0.50   0.45   0.35   0.28   0.22   0.19   0.16   0.14
  0.12   0.13   0.15   0.17   0.20   0.24   0.28   0.32   0.33   0.32   0.28   0.24   0.20   0.17   0.15   0.13
  0.11   0.12   0.14   0.16   0.18   0.20   0.22   0.24   0.25   0.24   0.22   0.20   0.18   0.16   0.14   0.12
  0.11   0.12   0.13   0.14   0.16   0.17   0.19   0.20   0.20   0.20   0.19   0.17   0.16   0.14   0.13   0.12
  0.10   0.11   0.12   0.13   0.14   0.15   0.16   0.16   0.17   0.16   0.16   0.15   0.14   0.13   0.12   0.11
  0.09   0.10   0.11   0.12   0.12   0.13   0.14   0.14   0.14   0.14   0.14   0.13   0.12   0.12   0.11   0.10

I can multiply each one by 255 to give me a range of values I can use to colour the pixel. and it works ! producing a radial gradient (that's only 16px in diameter for this example).

But when I want a bigger gradient lets say one inside a rectangle of 512*512. It wont work it will still produce the small gradient.

so for example if the screen was 512*512 pixel 0,0 would have a value of 256px left from center and 256px up from the center. which would give it a distance of 362.04px from the center (sqrt(256^2 + 256^2)). The inverse of that 1/362.04 which = 0.0027. so if I get that value in the integer range of 0 to 255 I get 0.0027 * 255 = 0.68. which gets culled to just 0.

so what do I do ? scale the numbers to have bigger values ? I'm out of my depth here!

I also have learning difficulty so if anyone could explain it all to my like I'm 5 or step by step like a debugger would that would be groovy !!