completed fog example (#18)

* complete fog example
as both fog and basic lighting need the light system it made sense
to seperate it out, there are a few functions from raymath
int rlmath.py

* added shaders custom uniform

* added shaders_texture_waves.py

* added shaders_texture_drawing.py

* bug fix - unwanted transparent effect!

Co-authored-by: codifies <nospam@antispam.com>

examples/shaders/shaders_fog.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""
+
+Example converted to Python from:
+http://bedroomcoders.co.uk/raylib-fog/
+
+     port to python completed by codifies - dont know who started it
+
+
+"""
+
+from raylib.static import rl, ffi
+from raylib.colors import *
+import math
+
+from rlmath import *
+from light_system import *
+
+rl.SetConfigFlags(rl.FLAG_MSAA_4X_HINT | rl.FLAG_WINDOW_RESIZABLE)
+rl.InitWindow(1280, 768, b'Fog Test')
+
+camera = ffi.new('struct Camera3D *', [
+    [6, 2, 6],
+    [0, .5, 0],
+    [0, 1, 0],
+    45,
+    rl.CAMERA_PERSPECTIVE
+])
+
+model = rl.LoadModelFromMesh(rl.GenMeshTorus(0.4, 1, 16, 32))
+model2 = rl.LoadModelFromMesh(rl.GenMeshCube(1, 1, 1))
+model3 = rl.LoadModelFromMesh(rl.GenMeshSphere(0.5, 32, 32))
+
+texture = rl.LoadTexture(b'resources/test.png')
+
+model.materials[0].maps[rl.MAP_DIFFUSE].texture = texture
+model2.materials[0].maps[rl.MAP_DIFFUSE].texture = texture
+model3.materials[0].maps[rl.MAP_DIFFUSE].texture = texture
+
+light = Light(LIGHT_POINT,  [ 0, 4, 0 ], Vector3Zero(), WHITE)
+lightSystem = LightSystem([ 0.2, 0.2, 0.2, 1.0 ], light)
+
+fog_color = ffi.new('float[]', [0.2,0.2,1.0,1.0])
+fogC = rl.GetShaderLocation(lightSystem.shader, b'fogColor')
+rl.SetShaderValue(lightSystem.shader, fogC, fog_color, rl.UNIFORM_VEC4);
+fogD = rl.GetShaderLocation(lightSystem.shader, b'FogDensity')
+fogDensity = 0.12
+
+model.materials[0].shader = lightSystem.shader
+model2.materials[0].shader = lightSystem.shader
+model3.materials[0].shader = lightSystem.shader
+
+rl.SetTargetFPS(60)
+a=0.0
+while not rl.WindowShouldClose():
+    
+    a+=0.01
+    camera.position.x = math.sin(a)*6
+    camera.position.z = math.cos(a)*6 
+    rl.UpdateCamera(camera)
+
+    lightSystem.update(camera.position)
+
+    
+    model.transform = MatrixMultiply(model.transform, MatrixRotateX(-0.025))[0]
+    model.transform = MatrixMultiply(model.transform, MatrixRotateZ(0.012))[0]
+    
+    if rl.IsKeyDown(rl.KEY_UP):
+        fogDensity = min(fogDensity + 0.001, 1)
+
+    if rl.IsKeyDown(rl.KEY_DOWN):
+        fogDensity = max(fogDensity - 0.001, 0)
+
+    rl.SetShaderValue(lightSystem.shader, fogD, ffi.new('float[]', [fogDensity]), rl.UNIFORM_FLOAT)
+
+    rl.BeginDrawing()
+
+    rl.ClearBackground([int(255 * i) for i in fog_color])
+    if rl.IsKeyDown(rl.KEY_SPACE):
+        rl.ClearBackground(BLACK)
+    
+    rl.BeginMode3D(camera[0])
+    rl.DrawModel(model, [0] * 3, 1, WHITE)
+    rl.DrawModel(model2, [-2.6, 0, 0], 1, WHITE)
+    rl.DrawModel(model3, [ 2.6, 0, 0], 1, WHITE)
+
+    for i in range(-20, 20, 2):
+        rl.DrawModel(model, [i, 0, 2], 1, WHITE)
+
+
+    rl.DrawGizmo([1000, 1000, 1000])
+
+    rl.EndMode3D()
+
+    rl.DrawFPS(10, 10)
+    rl.DrawText(f'Up/Down to change fog density: {fogDensity}'.encode('utf-8'), 10, 30, 20, WHITE)
+
+    rl.EndDrawing()
+
+rl.UnloadModel(model)
+rl.UnloadModel(model2)
+rl.UnloadModel(model3)
+rl.UnloadTexture(texture)
+rl.UnloadShader(lightSystem.shader)
+rl.CloseWindow()
+