nim-glm: A Nim repository from dawkot

#Nim-glm port for matrix-vector algebra with shader like syntax.

Nim-glm has vector constructors: Here's some examples

var
    v = vec3(1.0, 5.0, 6.0)
    a = vec3(2.0, 2.0, 5.0)
    v4 = vec4(v, 1.0);
    c = cross(v,a)
    m = rotate(mat4(), 5.0, vec3(1.0, 0.0, 0.0))
    r = v4 * m

Also, this version has basics for common matrices creations:

var
    eye = vec3(50.0, 50.0, 10.0)
    center = vec3(0.0)
    up = vec3(0.0, 1.0, 0.0)
    viewMatrix = lookAt(eye, center, up)
    projectionMat = perspective(math.PI/2, 1.0, 0.01, 100.0)

echo viewMatrix * projectionMat

Use it in OpenGL environment:

var modelView = mat4f(1)
  .rotate(alpha, n.x, n.y, n.z)
  .scale(4,5,6)
  .translate(1,2,3)

glUniformMatrix4fv(_uniformLocation, 1, false, modelView.caddr)

There is swizzling support:

var pos1,pos2: Vec4f
pos1.xyz = pos2.zww
pos1.yz += pos2.ww
var texcoord: Vec2f
echo texcoord.st
var color: Vec4f
color.rgb = color.bgr

matrices can be printed with echo, because they have the $ operator implemented. By default they use nice unicode characters for best visual representation. But if you have probmles with them, you can pass -d:noUnicode to the compiler and the $ functions will use a pure ASCII representation.

      ASCII            unicode

 / 3  7   3   0 \   ⎡3  7   3   0⎤
|  0  2  -1   1  |  ⎢0  2  -1   1⎥
|  5  4   3   2  |  ⎢5  4   3   2⎥
 \ 6  6   4  -1 /   ⎣6  6   4  -1⎦

perlin noise:

import glm/vec
import glm/noise

var line = newStringOfCap(80)
for y in 0 ..< 20:
  for x in 0 ..< 40:
    let n = perlin(vec2f(float32(x), float32(y)) * 0.1'f32)
    let i = int(floor((n + 1) * 5))
    line.add "  .:+=*%#@"[i]
  echo line
  line.setLen(0)


# expected output:
#
#  =+++:::::+======++++==*%%%%**==++++++++=
#  ===++::::++====++::++=*%%%%%*===++++:+++
#  ***=+::.::+====++:::+==*%%%%***==++:::::
#  ***=+:...:++===++:::++==**%%*****=++:...
#  **=+::...::+====++:::+++==********=+:.
#  *==+:....::+=====++:::::++==******=+:.
#  ==+:..  .::+=****=++:::::::+==*****=+:.
#  =+:..   .:++=*%%**=++::....:+==**%**=+:.
#  ++:.   ..:+=*%%%%**=+:..   .:+=**%%**=+:
#  ++:.   .::+=*%###%*=+::.   .:+==*%%%**=+
#  =+:..  .:+==*%###%*==+:.   .:+==*%%%%*==
#  =++:....:+=**%###%**=+:.    .:+=*%%#%%*=
#  ==+::..:++=*%%####%*=+:.    .:+=*%%#%%**
#  *==+:::++==*%%####%**=+:.   .:+==*%%%%**
#  **==++++==***%%##%%%**=+:....::+=*****==
#  %**======******%%%%%%**=+:....:++=***==+
#  ***===*****====****%%%*=+::...:++====+++
#  **===*****==++++==******=+::.::++====++:
#  *====*****=++:::++==****=+::::+++====++:
#  ==++==***==+::..::+======++::+++======++

Changes regarding based to C++glm and glsl
- the mod function is called floorMod instead. mod is already an operator in Nim and has it's own meaning that is very different to the meaning of the mod function in glsl. The name fmod is not good either, because fmod in c++ has a different meaning as well. The function floorMod from the math package has the same meaning as the mod function in glsl. Therefore mod is simply named floorMod to be at least consistent with the Nim standard library. The mod operator always rounds towards zero, I personally recommend to never use this operator.
- swizzle support. Unlike c++, Nim allows pretty well to implement swizzling. So it is implemented with the least amount of surprise.
- simd instructions are not implemented. You could hope that some day the C compiler will be smart enough to inject them, but I would not bet on it.
- glm in c++ has a lot more extensions that are not yet ported over to the Nim version. They are added when needed. On the other hand, this library is feature complete in terms of featurs that come from GLSL.

dawkot/nim-glm