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_drawing.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+
+
+from raylib.dynamic import raylib as rl, ffi
+from raylib.colors import *
+
+
+# a few functions ported from raymath
+from rlmath import *
+
+
+#// 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] example - basic lighting")
+
+camera = ffi.new('struct Camera3D *', [
+    [2, 12, 6],
+    [0, .5, 0],
+    [0, 1, 0],
+    45,
+    rl.CAMERA_PERSPECTIVE
+])
+
+imBlank = rl.GenImageColor(1024, 1024, BLANK)
+texture = rl.LoadTextureFromImage(imBlank)  #// Load blank texture to fill on shader
+rl.UnloadImage(imBlank);
+
+#// NOTE: Using GLSL 330 shader version, on OpenGL ES 2.0 use GLSL 100 shader version
+shader = rl.LoadShader(b"", b"resources/shaders/glsl330/cubes_panning.fs");
+
+time = ffi.new("float *", 0.0)
+timeLoc = rl.GetShaderLocation(shader, b"uTime");
+rl.SetShaderValue(shader, timeLoc, time, rl.UNIFORM_FLOAT);
+    
+
+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
+    #//----------------------------------------------------------------------------------
+    time[0] = rl.GetTime();
+    rl.SetShaderValue(shader, timeLoc, time, rl.UNIFORM_FLOAT);
+
+    #//----------------------------------------------------------------------------------
+
+    #// Draw
+    #//----------------------------------------------------------------------------------
+    rl.BeginDrawing()
+
+    rl.ClearBackground(RAYWHITE)
+
+    rl.BeginShaderMode(shader)    #// Enable our custom shader for next shapes/textures drawings
+    rl.DrawTexture(texture, 0, 0, WHITE)  #// Drawing BLANK texture, all magic happens on shader
+    rl.EndShaderMode()            #// Disable our custom shader, return to default shader
+
+    rl.DrawText(b"BACKGROUND is PAINTED and ANIMATED on SHADER!", 10, 10, 20, MAROON);
+
+
+    rl.EndDrawing()
+#//----------------------------------------------------------------------------------
+
+
+#// De-Initialization
+#//--------------------------------------------------------------------------------------
+
+
+rl.UnloadTexture(texture)     #// Unload the texture
+
+rl.CloseWindow()              #// Close window and OpenGL context