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/light_system.py

@@ -0,0 +1,99 @@
+from raylib.dynamic import raylib as rl, ffi
+
+
+class LightSystem:
+    MAX_LIGHTS = 4         #// Max dynamic lights supported by shader
+    lightsCount = 0
+    lights = []
+
+    def __init__(self, ambient = [ 0.2, 0.2, 0.2, 1.0 ], *ls):
+        self.shader = rl.LoadShader(b"resources/shaders/fogLight.vs",
+                            b"resources/shaders/fogLight.fs");
+
+        #// Get some shader loactions
+        self.shader.locs[rl.LOC_MATRIX_MODEL] = rl.GetShaderLocation(self.shader, b"matModel");
+        self.shader.locs[rl.LOC_VECTOR_VIEW] = rl.GetShaderLocation(self.shader, b"viewPos");
+
+        #// ambient light level
+        self.ambientLoc = rl.GetShaderLocation(self.shader, b"ambient");
+        v = ffi.new("struct Vector4 *", ambient)
+        rl.SetShaderValue(self.shader, self.ambientLoc, v, rl.UNIFORM_VEC4);
+
+        for light in ls:
+            self.add(light)
+
+    def add(self, light):
+        light.configure(len(self.lights), self.shader)
+        self.lights.append(light)
+        if len(self.lights) > self.MAX_LIGHTS:
+            raise Exception("Too many lights")
+
+    def update(self, cameraPos):
+        rl.SetShaderValue(self.shader, self.shader.locs[rl.LOC_VECTOR_VIEW], ffi.new("struct Vector3 *",cameraPos), rl.UNIFORM_VEC3)
+        for light in self.lights:
+            light.UpdateLightValues()
+
+    def draw(self):
+        for light in self.lights:
+            if light.enabled:
+                rl.DrawSphereEx(light.position[0], 0.2, 8, 8, light.color)
+
+
+
+
+LIGHT_DIRECTIONAL=0
+LIGHT_POINT=1
+
+
+class Light:
+    def __init__(self, type,  position,  target, color):
+        self.enabled = True
+        self.type = type
+        self.position = ffi.new("struct Vector3 *",position)
+        self.target = target
+        self.color = color
+
+
+
+
+    def configure(self, id, shader):
+        self.shader = shader
+        #// TODO: Below code doesn't look good to me,
+        #// it assumes a specific shader naming and structure
+        #// Probably this implementation could be improved
+        self.enabledName = f"lights[{id}].enabled"
+        self.typeName = f"lights[{id}].type"
+        self.posName = f"lights[{id}].position"
+        self.targetName = f"lights[{id}].target"
+        self.colorName = f"lights[{id}].color"
+
+        self.enabledLoc = rl.GetShaderLocation(shader, self.enabledName.encode('utf-8'))
+        self.typeLoc = rl.GetShaderLocation(shader, self.typeName.encode('utf-8'))
+        self.posLoc = rl.GetShaderLocation(shader, self.posName.encode('utf-8'))
+        self.targetLoc = rl.GetShaderLocation(shader, self.targetName.encode('utf-8'))
+        self.colorLoc = rl.GetShaderLocation(shader, self.colorName.encode('utf-8'))
+
+        self.UpdateLightValues()
+
+
+    #// Send light properties to shader
+    #// NOTE: Light shader locations should be available
+    def UpdateLightValues(self):
+        #// Send to shader light enabled state and type
+        rl.SetShaderValue(self.shader, self.enabledLoc, ffi.new("int *",self.enabled), rl.UNIFORM_INT)
+        rl.SetShaderValue(self.shader, self.typeLoc, ffi.new("int *",self.type), rl.UNIFORM_INT)
+
+        #// Send to shader light position values
+        position = [ self.position.x, self.position.y, self.position.z]
+        rl.SetShaderValue(self.shader, self.posLoc, ffi.new("struct Vector3 *",position), rl.UNIFORM_VEC3)
+
+        #// Send to shader light target position values
+        target =[  self.target.x, self.target.y, self.target.z ]
+        rl.SetShaderValue(self.shader, self.targetLoc, ffi.new("struct Vector3 *",target), rl.UNIFORM_VEC3)
+
+        #// Send to shader light color values
+        color = [self.color[0]/255.0, self.color[1]/255.0,  self.color[2]/255.0, self.color[3]/255.0]
+        rl.SetShaderValue(self.shader, self.colorLoc, ffi.new("struct Vector4 *",color), rl.UNIFORM_VEC4)
+
+
+