///////////////////////////////////////////////////////////
// Attributes
attribute vec3 a_position;
attribute vec2 a_texCoord;
attribute vec4 a_color;

///////////////////////////////////////////////////////////
// Uniforms
uniform mat4 u_projectionMatrix;

///////////////////////////////////////////////////////////
// Varyings
varying vec2 v_texCoord;
varying vec4 v_color;

#if defined(TEXTURE_REPEAT)
uniform vec2 u_textureRepeat;
#endif

#if defined(TEXTURE_OFFSET)
uniform vec2 u_textureOffset;
#endif


#if defined(NO_Z_FIGHTING)
// Éî¶ÈÆ«ÒÆÖµ
uniform float u_depthOffset;
#endif


varying float v_fogFactor;						//fog factor
//fog parameter
uniform vec4 u_fogparam; // .x, .y, .z, .w stand for fog density, fog start, fog end, fog type. fog type 0, no fog, fog type 1 linear fog, fog type 2 exp fog, fog type 3 exp2 fog

void main()
{
    gl_Position = u_projectionMatrix * vec4(a_position, 1);
    v_texCoord = a_texCoord;
    v_color = a_color;

	#if defined(NO_Z_FIGHTING)
		gl_Position.z -= u_depthOffset;
	#endif
	
    #if defined(TEXTURE_REPEAT)
		v_texCoord *= u_textureRepeat;
    #endif
    
    #if defined(TEXTURE_OFFSET)
		v_texCoord += u_textureOffset;
    #endif
    
	#if defined(FOG)
	// linear fog
	#if FOG == 1
	float z = gl_Position.z;//(u_worldViewMatrix * position).z;
	v_fogFactor = (u_fogparam.z - z) / (u_fogparam.z - u_fogparam.y);
	v_fogFactor = clamp(v_fogFactor, 0.0, 1.0); 
	// exp fog
	#elif FOG == 2
	float z = gl_Position.z;//(u_worldViewMatrix * position).z;
	const float LOG2 = 1.442695;
	v_fogFactor = exp2( -u_fogparam.x * 
			   z * 
			   LOG2 );
	v_fogFactor = clamp(v_fogFactor, 0.0, 1.0); 
	// exp2 fog
	#elif FOG == 3
	float z = gl_Position.z;//(u_worldViewMatrix * position).z;
	const float LOG2 = 1.442695;
	v_fogFactor = exp2( -u_fogparam.x * 
			   u_fogparam.x * 
			   z * 
			   z * 
			   LOG2 );
	v_fogFactor = clamp(v_fogFactor, 0.0, 1.0); 
	#endif
	#endif
}