4. Using Textures
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
In this chapter, we will cover:
- Applying a 2D texture
- Applying multiple textures
- Using alpha maps to discard pixels
- Using normal maps
- Simulating reflection with cube maps
- Simulating refraction with cube maps
- Applying a projected texture
- Rendering to a texture
- Using sampler objects
Textures are an important and fundamental aspect of real-time rendering in general, and OpenGL in particular. The use of textures within a shader opens up a huge range of possibilities. Beyond just using textures as sources of color information, they can be used for things like depth information, shading parameters, displacement maps, normal vectors, or other vertex data. The list is virtually endless. Textures are among the most widely used tools for advanced effects in OpenGL programs, and that isn't likely to change anytime soon.
Note
In OpenGL 4, we now have the ability to read and write to memory via buffer textures, shader storage buffer objects, and image textures (image load/store). This further muddies the waters of what exactly defines a texture. In general, we might just think of it as a buffer of data that may or may not contain an image.
OpenGL 4.2 introduced immutable storage textures. Despite what the term may imply, immutable storage textures are not textures that can't change. Instead, the term immutable refers to the fact that, once the texture is allocated, the storage cannot be changed. That is, the size, format, and number of layers are fixed, but the texture content itself can be modified. The word immutable refers to the allocation of the memory, not the contents of the memory. Immutable storage textures are preferable in the vast majority of cases because of the fact that many run-time (draw-time) consistency checks can be avoided, and you include a certain degree of "type safety," since we can't accidentally change the allocation of a texture. Throughout this book, we'll use immutable storage textures exclusively.
In this chapter, we'll look at some basic and advanced texturing techniques. We'll start with the basics, just applying color textures, and move on to using textures as normal maps and environment maps. With environment maps, we can simulate things like reflection and refraction. We'll see an example of projecting a texture onto objects in a scene similar to the way that a slide projector projects an image. Finally, we'll wrap up with an example of rendering directly to a texture(using framebuffer objects (FBOs) and then applying that texture to an object.
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