Supermodel/Src/Graphics/New3D/R3DScrollFog.cpp

#include "R3DScrollFog.h"
#include "Graphics/Shader.h"

namespace New3D {

static const char *vertexShaderFog = R"glsl(

#version 410 core

void main(void)
{
	const vec4 vertices[] = vec4[](vec4(-1.0, -1.0, 0.0, 1.0),
									vec4(-1.0,  1.0, 0.0, 1.0),
									vec4( 1.0, -1.0, 0.0, 1.0),
									vec4( 1.0,  1.0, 0.0, 1.0));

	gl_Position = vertices[gl_VertexID % 4];
}

)glsl";

static const char *fragmentShaderFog = R"glsl(

#version 410 core

uniform float	fogAttenuation;
uniform float	fogAmbient;
uniform vec4	fogColour;

// outputs
layout(location = 0) out vec4 out0;		// opaque
layout(location = 1) out vec4 out1;		// trans layer 1
layout(location = 2) out vec4 out2;		// trans layer 2

void WriteOutputs(vec4 colour)
{
	vec4 blank = vec4(0.0);
	
	out0 = colour;
	out1 = blank;
	out2 = blank;	
}

void main()
{
	// Scroll fog base color
	vec3 lFogColor = fogColour.rgb * fogAmbient;

	// Scroll fog density
	vec4 scrollFog = vec4(lFogColor, fogColour.a * (1.0 - fogAttenuation));

	// Final Color
	WriteOutputs(scrollFog);
}

)glsl";


R3DScrollFog::R3DScrollFog(const Util::Config::Node &config)
  : m_config(config),
	m_vao(0)
{
	m_shaderProgram		= 0;
	m_vertexShader		= 0;
	m_fragmentShader	= 0;

	AllocResources();

	glGenVertexArrays(1, &m_vao);
	glBindVertexArray(m_vao);
	// no states needed since we do it in the shader
	glBindVertexArray(0);
}

R3DScrollFog::~R3DScrollFog()
{
	DeallocResources();

	if (m_vao) {
		glDeleteVertexArrays(1, &m_vao);
		m_vao = 0;
	}
}

void R3DScrollFog::DrawScrollFog(float rgba[4], float attenuation, float ambient)
{
	// some ogl states
	glDepthMask			(GL_FALSE);			// disable z writes
	glDisable			(GL_DEPTH_TEST);	// disable depth testing

	glBindVertexArray	(m_vao);
	glUseProgram		(m_shaderProgram);
	glUniform4fv		(m_locFogColour, 1, rgba);
	glUniform1f			(m_locFogAttenuation, attenuation);
	glUniform1f			(m_locFogAmbient, ambient);

	glDrawArrays		(GL_TRIANGLE_STRIP, 0, 4);

	glUseProgram		(0);
	glBindVertexArray	(0);

	glDisable			(GL_BLEND);
	glDepthMask			(GL_TRUE);
}

void R3DScrollFog::AllocResources()
{
	bool success = LoadShaderProgram(&m_shaderProgram, &m_vertexShader, &m_fragmentShader, m_config["VertexShaderFog"].ValueAs<std::string>(), m_config["FragmentShaderFog"].ValueAs<std::string>(), vertexShaderFog, fragmentShaderFog);

	m_locFogColour		= glGetUniformLocation(m_shaderProgram, "fogColour");
	m_locFogAttenuation	= glGetUniformLocation(m_shaderProgram, "fogAttenuation");
	m_locFogAmbient		= glGetUniformLocation(m_shaderProgram, "fogAmbient");
}

void R3DScrollFog::DeallocResources()
{
	if (m_shaderProgram) {
		DestroyShaderProgram(m_shaderProgram, m_vertexShader, m_fragmentShader);
	}

	m_shaderProgram		= 0;
	m_vertexShader		= 0;
	m_fragmentShader	= 0;
}

}