Simulating smoke with particles
by William C. Y. Lo, Raymond C. H. Lo, David Wolff, Muhammad Mobeen Movania
OpenGL – Build high performance graphics
- OpenGL – Build high performance graphics
- Table of Contents
- OpenGL – Build high performance graphics
- OpenGL – Build high performance graphics
- Credits
- Preface
- 1. Module 1
- 1. Introduction to Modern OpenGL
- Introduction
- Setting up the OpenGL v3.3 core profile on Visual Studio 2010 using the GLEW and freeglut libraries
- Designing a GLSL shader class
- Rendering a simple colored triangle using shaders
- Doing a ripple mesh deformer using the vertex shader
- Dynamically subdividing a plane using the geometry shader
- Dynamically subdividing a plane using the geometry shader with instanced rendering
- Drawing a 2D image in a window using the fragment shader and the SOIL image loading library
- 2. 3D Viewing and Object Picking
- Introduction
- Implementing a vector-based camera with FPS style input support
- Implementing the free camera
- Implementing the target camera
- Implementing view frustum culling
- Implementing object picking using the depth buffer
- Implementing object picking using color
- Implementing object picking using scene intersection queries
- 3. Offscreen Rendering and Environment Mapping
- Introduction
- Implementing the twirl filter using the fragment shader
- Rendering a skybox using static cube mapping
- Implementing a mirror with render-to-texture using FBO
- Rendering a reflective object using dynamic cube mapping
- Implementing area filtering (sharpening/blurring/embossing) on an image using convolution
- Implementing the glow effect
- 4. Lights and Shadows
- Introduction
- Implementing per-vertex and per-fragment point lighting
- Implementing per-fragment directional light
- Implementing per-fragment point light with attenuation
- Implementing per-fragment spot light
- Implementing shadow mapping with FBO
- Implemeting shadow mapping with percentage closer filtering (PCF)
- Implementing variance shadow mapping
- 5. Mesh Model Formats and Particle Systems
- 6. GPU-based Alpha Blending and Global Illumination
- Introduction
- Implementing order-independent transparency using front-to-back peeling
- Implementing order-independent transparency using dual depth peeling
- Implementing screen space ambient occlusion (SSAO)
- Implementing global illumination using spherical harmonics lighting
- Implementing GPU-based ray tracing
- Implementing GPU-based path tracing
- 7. GPU-based Volume Rendering Techniques
- Introduction
- Implementing volume rendering using 3D texture slicing
- Implementing volume rendering using single-pass GPU ray casting
- Implementing pseudo-isosurface rendering in single-pass GPU ray casting
- Implementing volume rendering using splatting
- Implementing transfer function for volume classification
- Implementing polygonal isosurface extraction using the Marching Tetrahedra algorithm
- Implementing volumetric lighting using the half-angle slicing
- 8. Skeletal and Physically-based Simulation on the GPU
- Introduction
- Implementing skeletal animation using matrix palette skinning
- Implementing skeletal animation using dual quaternion skinning
- Modeling cloth using transform feedback
- Implementing collision detection and response on a transform feedback-based cloth model
- Implementing a particle system using transform feedback
- 1. Introduction to Modern OpenGL
- 2. Module 2
- 1. Getting Started with GLSL
- Introduction
- Using a function loader to access the latest OpenGL functionality
- Using GLM for mathematics
- Determining the GLSL and OpenGL version
- Compiling a shader
- Linking a shader program
- Sending data to a shader using vertex attributes and vertex buffer objects
- Getting a list of active vertex input attributes and locations
- Sending data to a shader using uniform variables
- Getting a list of active uniform variables
- Using uniform blocks and uniform buffer objects
- Getting debug messages
- Building a C++ shader program class
- 2. The Basics of GLSL Shaders
- Introduction
- Implementing diffuse, per-vertex shading with a single point light source
- Implementing per-vertex ambient, diffuse, and specular (ADS) shading
- Using functions in shaders
- Implementing two-sided shading
- Implementing flat shading
- Using subroutines to select shader functionality
- Discarding fragments to create a perforated look
- 3. Lighting, Shading, and Optimization
- 4. Using Textures
- 5. Image Processing and Screen Space Techniques
- 6. Using Geometry and Tessellation Shaders
- 7. Shadows
- 8. Using Noise in Shaders
- 9. Particle Systems and Animation
- 10. Using Compute Shaders
- 1. Getting Started with GLSL
- 3. Module 3
- 1. Getting Started with OpenGL
- Introduction
- Setting up a Windows-based development platform
- Setting up a Mac-based development platform
- Setting up a Linux-based development platform
- Installing the GLFW library in Windows
- Installing the GLFW library in Mac OS X and Linux
- Creating your first OpenGL application with GLFW
- Compiling and running your first OpenGL application in Windows
- Compiling and running your first OpenGL application in Mac OS X or Linux
- 2. OpenGL Primitives and 2D Data Visualization
- 3. Interactive 3D Data Visualization
- 4. Rendering 2D Images and Videos with Texture Mapping
- Introduction
- Getting started with modern OpenGL (3.2 or higher)
- Setting up the GLEW, GLM, SOIL, and OpenCV libraries in Windows
- Setting up the GLEW, GLM, SOIL, and OpenCV libraries in Mac OS X/Linux
- Creating your first vertex and fragment shader using GLSL
- Rendering 2D images with texture mapping
- Real-time video rendering with filters
- 5. Rendering of Point Cloud Data for 3D Range-sensing Cameras
- 6. Rendering Stereoscopic 3D Models using OpenGL
- 7. An Introduction to Real-time Graphics Rendering on a Mobile Platform using OpenGL ES 3.0
- 8. Interactive Real-time Data Visualization on Mobile Devices
- 9. Augmented Reality-based Visualization on Mobile or Wearable Platforms
- A. Bibliography
- 1. Getting Started with OpenGL
- Index
Smoke is characterized by many small particles that float away from the source, and spread out as they move through the air. We can simulate the floatation effect with particles by using a small upwards acceleration (or constant velocity), but simulating the diffusion of each small smoke particle would be too expensive. Instead, we can simulate the diffusion of many small particles by making our simulated particles change their size (grow) over time.
The following image shows an example of the results:
The texture for each particle is a very light "smudge" of grey or black color.
To make the particles grow over time, we'll make use of the GL_PROGRAM_POINT_SIZE functionality in OpenGL, which allows us to modify the point size within the vertex shader.
Note
Alternatively, we could draw quads, or use the geometry shader to generate the quads using the technique demonstrated in Chapter 6, Using Geometry and Tessellation Shaders.
Start with the basic particle system presented in the recipe Creating a particle system using transform feedback.
Set the uniform variable Accel to a small upward value like (0.0, 0.1, 0.0).
Set the uniform variable ParticleLifetime to about six seconds.
Create and load a texture for the particles that looks like just light grey smudge. Bind it to texture unit zero, and set the uniform ParticleTex to zero.
Set the uniform variables MinParticleSize and MaxParticleSize to 10 and 200 respectively.
Use the following steps:
- Set the initial positions to the origin. Define the initial velocities in the same way as described in the recipe Creating a particle system using transform feedback. However, it looks best when you use a large variance in
theta. - Within the vertex shader, add the following uniforms:
uniform float MinParticleSize; uniform float MaxParticleSize;
- Also within the vertex shader, use the following code for the
renderfunction:subroutine (RenderPassType) void render() { float age = Time - VertexStartTime; Transp = 0.0; if( Time >= VertexStartTime ) { float agePct = age/ParticleLifetime; Transp = 1.0 - agePct; gl_PointSize = mix(MinParticleSize,MaxParticleSize,agePct); } gl_Position = MVP * vec4(VertexPosition, 1.0); } - In the main OpenGL application, before rendering your particles, make sure to enable
GL_PROGRAM_POINT_SIZE:glEnable(GL_PROGRAM_POINT_SIZE);
The render subroutine function sets the built-in variable gl_PointSize to a value between MinParticleSize and MaxParticleSize, determined by the age of the particle. This causes the size of the particles to grow as they evolve through the system.
Note that the variable gl_PointSize is ignored by OpenGL unless GL_PROGRAM_POINT_SIZE is enabled.
-
No Comment