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_custom_uniform.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+
+
+from raylib.dynamic import raylib as rl, ffi
+from raylib.colors import *
+import math
+
+# 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
+])
+
+model = rl.LoadModel(b"resources/models/barracks.obj")                  # // Load OBJ model
+texture = rl.LoadTexture(b"resources/models/barracks_diffuse.png")      # // Load model texture (diffuse map)
+
+#// Assign texture to default model material
+model.materials[0].maps[rl.MAP_DIFFUSE].texture = texture
+#// NOTE: Defining 0 (NULL) for vertex shader forces usage of internal default vertex shader
+shader = rl.LoadShader(b"", b"resources/shaders/glsl330/swirl.fs")
+swirlCenterLoc = rl.GetShaderLocation(shader, b"center")
+angle = 6.282;
+
+
+
+swirl = ffi.new("struct Vector2 *", [0,0])
+
+target = rl.LoadRenderTexture(screenWidth, screenHeight)
+
+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
+    #//----------------------------------------------------------------------------------
+
+    angle -= 0.002
+    camera.position.x = math.sin(angle) * 30.0
+    camera.position.z = math.cos(angle) * 30.0
+    rl.UpdateCamera(camera)              #// Update camera
+
+    swirl.x = rl.GetMouseX()
+    swirl.y = screenHeight - rl.GetMouseY()
+    rl.SetShaderValue(shader, swirlCenterLoc, swirl, rl.UNIFORM_VEC2);
+    #//----------------------------------------------------------------------------------
+
+    #// Draw
+    #//----------------------------------------------------------------------------------
+    rl.BeginDrawing()
+
+
+    rl.BeginTextureMode(target)
+    rl.ClearBackground(RAYWHITE)
+    rl.BeginMode3D(camera[0])
+
+    #// Draw the three models
+    rl.DrawModel(model, [0,0,0], 1.0, WHITE)
+
+    rl.DrawGrid(10, 1.0)
+
+    rl.EndTextureMode()
+    rl.EndMode3D()
+    
+    rl.BeginShaderMode(shader)
+    #// NOTE: Render texture must be y-flipped due to default OpenGL coordinates (left-bottom)
+    rl.DrawTextureRec(target.texture, [ 0, 0, target.texture.width,-target.texture.height], [0.0], WHITE)
+    rl.EndShaderMode()
+    #// Draw some 2d text over drawn texture
+    rl.DrawText(b"(c) Barracks 3D model by Alberto Cano", screenWidth - 220, screenHeight - 20, 10, GRAY);
+
+    
+    rl.DrawFPS(10, 10)
+
+    rl.EndDrawing()
+#//----------------------------------------------------------------------------------
+
+
+#// De-Initialization
+#//--------------------------------------------------------------------------------------
+rl.UnloadModel(model) #        // Unload the model
+
+rl.UnloadTexture(texture)     #// Unload the texture
+
+rl.CloseWindow()              #// Close window and OpenGL context