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_texture_waves.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python3
+
+from raylib.static import rl, ffi
+from raylib.colors import *
+import math
+
+# a few functions ported from raymath
+from rlmath import *
+
+from ctypes import byref
+
+#// Initialization
+#//--------------------------------------------------------------------------------------
+screenWidth = 800;
+screenHeight = 450;
+
+rl.SetConfigFlags(rl.FLAG_MSAA_4X_HINT| rl.FLAG_WINDOW_RESIZABLE);  # Enable Multi Sampling Anti Aliasing 4x (if available)
+rl.InitWindow(screenWidth, screenHeight, b"raylib [shaders]")
+
+camera = ffi.new('struct Camera3D *', [
+    [2, 12, 6],
+    [0, .5, 0],
+    [0, 1, 0],
+    45,
+    rl.CAMERA_PERSPECTIVE
+])
+
+texture = rl.LoadTexture(b"resources/space.png")
+
+shader = rl.LoadShader(b"", b"resources/shaders/glsl330/wave.fs")
+secondsLoc = rl.GetShaderLocation(shader, b"secondes")
+freqXLoc = rl.GetShaderLocation(shader, b"freqX")
+freqYLoc = rl.GetShaderLocation(shader, b"freqY")
+ampXLoc = rl.GetShaderLocation(shader, b"ampX")
+ampYLoc = rl.GetShaderLocation(shader, b"ampY")
+speedXLoc = rl.GetShaderLocation(shader, b"speedX")
+speedYLoc = rl.GetShaderLocation(shader, b"speedY")
+
+freqX = ffi.new("float *", 25.0)
+freqY = ffi.new("float *", 25.0)
+ampX = ffi.new("float *", 5.0)
+ampY = ffi.new("float *", 5.0)
+speedX = ffi.new("float *", 8.0)
+speedY = ffi.new("float *", 8.0)
+
+screenSize = ffi.new("struct Vector2 *",[ rl.GetScreenWidth(), rl.GetScreenHeight() ])
+rl.SetShaderValue(shader, rl.GetShaderLocation(shader, b"size"), screenSize, rl.UNIFORM_VEC2)
+
+rl.SetShaderValue(shader, freqXLoc, freqX, rl.UNIFORM_FLOAT)
+rl.SetShaderValue(shader, freqYLoc, freqY, rl.UNIFORM_FLOAT)
+rl.SetShaderValue(shader, ampXLoc, ampX, rl.UNIFORM_FLOAT)
+rl.SetShaderValue(shader, ampYLoc, ampY, rl.UNIFORM_FLOAT)
+rl.SetShaderValue(shader, speedXLoc, speedX, rl.UNIFORM_FLOAT)
+rl.SetShaderValue(shader, speedYLoc, speedY, rl.UNIFORM_FLOAT)
+    
+seconds = ffi.new("float *", 0.0)   
+
+rl.SetTargetFPS(60)                      # // Set our game to run at 60 frames-per-second
+#//--------------------------------------------------------------------------------------
+
+#// Main game loop
+while not rl.WindowShouldClose():            #// Detect window close button or ESC key
+    #// Update
+    #//----------------------------------------------------------------------------------
+    seconds[0] += rl.GetFrameTime()
+    rl.SetShaderValue(shader, secondsLoc, seconds, rl.UNIFORM_FLOAT)
+    #//----------------------------------------------------------------------------------
+
+    #// Draw
+    #//----------------------------------------------------------------------------------
+    rl.BeginDrawing()
+
+
+    rl.ClearBackground(RAYWHITE)
+    rl.BeginShaderMode(shader);
+    
+    rl.DrawTexture(texture, 0, 0, WHITE);
+    rl.DrawTexture(texture, texture.width, 0, WHITE);
+        
+    rl.EndShaderMode();
+
+    rl.EndDrawing()
+#//----------------------------------------------------------------------------------
+
+
+#// De-Initialization
+#//--------------------------------------------------------------------------------------
+
+
+rl.CloseWindow()              #// Close window and OpenGL context