/
HierarchicalSampleWarping.java
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/
HierarchicalSampleWarping.java
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package org.lwjgl.demo.opengl.sampling;
import org.lwjgl.BufferUtils;
import org.lwjgl.demo.opengl.util.DemoUtils;
import org.lwjgl.glfw.GLFWKeyCallback;
import org.lwjgl.opengl.GL;
import org.lwjgl.system.MemoryStack;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import static org.lwjgl.demo.util.IOUtils.ioResourceToByteBuffer;
import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL33C.*;
import static org.lwjgl.stb.STBImage.*;
import static org.lwjgl.system.MemoryStack.stackPush;
import static org.lwjgl.system.MemoryUtil.NULL;
import static org.lwjgl.system.MemoryUtil.memAddress;
/**
* Demo showcasing Hierarchical Sample Warping (HSW) as first proposed in the paper
* "Wavelet Importance: Efficiently Evaluating Products of Complex Functions" by Clarberg et al.
* <p>
* This demo implements importance sampling via hierarchical sample warping in its associated fragment shader
* by using a 2D lightmap texture and generating samples with probabilities proportional to a texel's luminance.
* <p>
* See:
* <ul>
* <li><a href="https://link.springer.com/content/pdf/10.1007/978-1-4842-4427-2_16.pdf">section 16.4.2.3 HIERARCHICAL TRANSFORMATION in chapter "Transformations Zoo" of "Ray Tracing Gems".</a></li>
* <li><a href="http://graphics.ucsd.edu/~henrik/papers/wavelet_importance_sampling.pdf">"Wavelet Importance: Efficiently Evaluating Products of Complex Functions" by Clarberg et al.</a></li>
* <li><a href="https://www.ea.com/seed/news/siggraph21-global-illumination-surfels">SIGGRAPH 21: Global Illumination Based on Surfels</a></li>
* </ul>
*
* @author Kai Burjack
*/
public class HierarchicalSampleWarping {
private static int width = 800, height = 800;
public static void main(String[] args) throws IOException {
if (!glfwInit())
throw new IllegalStateException("Unable to initialize GLFW");
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
long window = glfwCreateWindow(width, height, "Hello HSW!", NULL, NULL);
if (window == NULL)
throw new RuntimeException("Failed to create the GLFW window");
glfwSetKeyCallback(window, new GLFWKeyCallback() {
public void invoke(long window, int key, int scancode, int action, int mods) {
if (action != GLFW_RELEASE)
return;
if (key == GLFW_KEY_ESCAPE)
glfwSetWindowShouldClose(window, true);
}
});
glfwMakeContextCurrent(window);
glfwSwapInterval(1);
GL.createCapabilities();
// Read actualy framebuffer size for HiDPI displays
try (MemoryStack stack = stackPush()) {
IntBuffer framebufferSize = stack.mallocInt(2);
nglfwGetFramebufferSize(window, memAddress(framebufferSize), memAddress(framebufferSize) + 4);
width = framebufferSize.get(0);
height = framebufferSize.get(1);
}
// Create shader program which implements visualization of the hierarchical sample warping
int program = glCreateProgram();
{
int vshader = DemoUtils.createShader("org/lwjgl/demo/opengl/sampling/hsw.vs.glsl", GL_VERTEX_SHADER, null);
int fshader = DemoUtils.createShader("org/lwjgl/demo/opengl/sampling/hsw.fs.glsl", GL_FRAGMENT_SHADER, null);
glAttachShader(program, vshader);
glAttachShader(program, fshader);
glBindFragDataLocation(program, 0, "color");
glLinkProgram(program);
int linked = glGetProgrami(program, GL_LINK_STATUS);
String programLog = glGetProgramInfoLog(program);
if (programLog.trim().length() > 0)
System.err.println(programLog);
if (linked == 0)
throw new AssertionError("Could not link program");
}
glUseProgram(program);
glUniform1i(glGetUniformLocation(program, "tex"), 0);
int timeLocation = glGetUniformLocation(program, "time");
int blendFactorLocation = glGetUniformLocation(program, "blendFactor");
// Create empty VAO
int vao = glGenVertexArrays();
glBindVertexArray(vao);
// Create FBO with 32-bit floating point color buffer to do the sample accumulation
int fbo = glGenFramebuffers();
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
int framebufferTex = glGenTextures();
{
glBindTexture(GL_TEXTURE_2D, framebufferTex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, width, height, 0, GL_RGBA, GL_FLOAT, (ByteBuffer) null);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, framebufferTex, 0);
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
throw new AssertionError("Incomplete framebuffer");
}
// Load an image, that we want to sample via hierarchical sample warping, into a texture
// and generate mipmaps for it
int tex = glGenTextures();
{
glBindTexture(GL_TEXTURE_2D, tex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
IntBuffer w = BufferUtils.createIntBuffer(1);
IntBuffer h = BufferUtils.createIntBuffer(1);
IntBuffer comp = BufferUtils.createIntBuffer(1);
ByteBuffer imageBuffer = ioResourceToByteBuffer("org/lwjgl/demo/opengl/sampling/env-square2.hdr", 64 * 1024);
stbi_set_flip_vertically_on_load(true);
if (!stbi_info_from_memory(imageBuffer, w, h, comp))
throw new IOException("Failed to read image information: " + stbi_failure_reason());
FloatBuffer image = stbi_loadf_from_memory(imageBuffer, w, h, comp, 3);
if (image == null)
throw new IOException("Failed to load image: " + stbi_failure_reason());
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB32F, w.get(0), h.get(0), 0, GL_RGB, GL_FLOAT, (ByteBuffer) null);
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, w.get(0), h.get(0), GL_RGB, GL_FLOAT, image);
stbi_image_free(image);
glGenerateMipmap(GL_TEXTURE_2D);
}
glfwShowWindow(window);
long lastTime = System.nanoTime();
float time = 0.0f;
int frameNumber = 0;
// Enable blending for sample accumulation in the FBO
glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_SRC_ALPHA);
glEnable(GL_BLEND);
while (!glfwWindowShouldClose(window)) {
glfwPollEvents();
long thisTime = System.nanoTime();
float elapsed = (thisTime - lastTime) / 1E9f;
time += elapsed;
lastTime = thisTime;
glViewport(0, 0, width, height);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
glUseProgram(program);
glBindTexture(GL_TEXTURE_2D, tex);
glUniform1f(blendFactorLocation, frameNumber / (frameNumber + 1.0f));
glUniform1f(timeLocation, time);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindFramebuffer(GL_READ_FRAMEBUFFER, fbo);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
glBlitFramebuffer(0, 0, width, height, 0, 0, width, height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
glfwSwapBuffers(window);
frameNumber++;
}
}
}