shader-effect.php

<?php

use Mammoth\Graphic\ImageLoader;

require 'bootstrap.php';
require 'vendor/autoload.php';

// Shader sources
$vertexSource = <<<GLSL
#version 150 core

in vec2 position;
in vec2 texcoord;

out vec2 Texcoord;

void main() {
	Texcoord = texcoord;
	gl_Position = vec4(position, 0.0, 1.0);
}
GLSL;
$fragmentSource = <<<GLSL
#version 150 core

in vec2 Texcoord;

uniform sampler2D texKitten;
uniform sampler2D texPuppy;
uniform float time;

out vec4 outColor;

void main() {
	float factor = (sin(time * 3.0) + 1.0) / 2.0;
	outColor = mix(texture(texKitten, Texcoord), texture(texPuppy, Texcoord), factor);
	if (Texcoord.y < 0.6)
		outColor = texture(texKitten, Texcoord);
	else
		outColor = texture(texKitten, vec2(Texcoord.x + sin(Texcoord.y * 60.0 + time * 2.0) / 30.0, 1.0 - Texcoord.y)) * vec4(0.7, 0.7, 1.0, 1.0);
}
GLSL;

SDL_Init(SDL_INIT_EVERYTHING);

SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

$window = SDL_CreateWindow("Shader effect", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
SDL_GL_CreateContext($window);

// Create Vertex Array Object
glGenVertexArrays(1, $vaos);
$vao = $vaos[0];
glBindVertexArray($vao);

// Create a Vertex Buffer Object and copy the vertex data to it
glGenBuffers(1, $vbos);
$vbo = $vbos[0];

$vertices = [
    //  Position      Color             Texcoords
    -0.5,  0.5, 1.0, 0.0, 0.0, 0.0, 0.0, // Top-left
    0.5,  0.5, 0.0, 1.0, 0.0, 1.0, 0.0, // Top-right
    0.5, -0.5, 0.0, 0.0, 1.0, 1.0, 1.0, // Bottom-right
    -0.5, -0.5, 1.0, 1.0, 1.0, 0.0, 1.0  // Bottom-left
];

glBindBuffer(GL_ARRAY_BUFFER, $vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof($vertices) * 4, $vertices, GL_STATIC_DRAW);

// Create an element array
glGenBuffers(1, $ebos);
$ebo = $ebos[0];

$elements = [
    0, 1, 2,
    2, 3, 0
];

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, $ebo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof($elements) * 4, $elements, GL_STATIC_DRAW);

// Create and compile the vertex shader
$vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource($vertexShader, 1, $vertexSource, NULL);
glCompileShader($vertexShader);

// Create and compile the fragment shader
$fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource($fragmentShader, 1, $fragmentSource, NULL);
glCompileShader($fragmentShader);

// Link the vertex and fragment shader into a shader program
$shaderProgram = glCreateProgram();
glAttachShader($shaderProgram, $vertexShader);
glAttachShader($shaderProgram, $fragmentShader);
glBindFragDataLocation($shaderProgram, 0, "outColor");
glLinkProgram($shaderProgram);
glUseProgram($shaderProgram);

// Specify the layout of the vertex data
$posAttrib = glGetAttribLocation($shaderProgram, "position");
glEnableVertexAttribArray($posAttrib);
glVertexAttribPointer($posAttrib, 2, GL_FLOAT, GL_FALSE, 7 * 4, 0);


$texAttrib = glGetAttribLocation($shaderProgram, "texcoord");
glEnableVertexAttribArray($texAttrib);
glVertexAttribPointer($texAttrib, 2, GL_FLOAT, GL_FALSE, 7 * 4, (5 * 4));

$imageLoader = new ImageLoader;

// Load textures
$textures = [];
glGenTextures(2, $textures);

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, $textures[0]);
$image = $imageLoader->load("textures/sample.png", $width, $height);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, $width, $height, 0, GL_RGBA, GL_UNSIGNED_BYTE, $image);
glUniform1i(glGetUniformLocation($shaderProgram, "texKitten"), 0);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);


glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, $textures[1]);
$image = $imageLoader->load("textures/sample2.png", $width, $height);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, $width, $height, 0, GL_RGBA, GL_UNSIGNED_BYTE, $image);
glUniform1i(glGetUniformLocation($shaderProgram, "texPuppy"), 1);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

$a = 0.0;

$start = microtime(true);

$event = new SDL_Event;

$quit = false;
while (!$quit) {
    // Clear the screen to black
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

    $a += 0.05;

    // Draw a rectangle from the 2 triangles using 6 indices
    glUniform1f(glGetUniformLocation($shaderProgram, "time"), $a);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, null);

    // Swap buffers
    SDL_GL_SwapWindow($window);
    while (SDL_PollEvent($event)) {
        if ($event->type == SDL_KEYDOWN) $quit = true;
    }

    SDL_Delay(10);
}


glDeleteTextures(2, $textures);

glDeleteProgram($shaderProgram);
glDeleteShader($fragmentShader);
glDeleteShader($vertexShader);

glDeleteBuffers(1, $ebo);
glDeleteBuffers(1, $vbo);

glDeleteVertexArrays(1, $vao);