3D GRAPHICS USING OPENGL ES 2 0

10.4 EXTENSIONS
OpenGL ES inherits the extension mechanism of the desktop OpenGL. Any vendor can create their own extensions to the basic behavior. Additionally, the OpenGL ES specifica- tion defines a few optional extensions that are likely to be implemented by[r]

All implementations should provide at least one configuration that supports rendering into a window surface, and has at least 16 bits of color buffer and 15 bits of depth buffer resolution. However, all other bets are off. For example, the implementation may offer you only configurations that have zer[r]

272 INTRODUCING M3G C H A P T E R 12
but some implementations use tailor-made software rasterizers instead. All hardware- accelerated devices are probably using OpenGL ES, though.
Finally, at the bottom right of Figure 12.1, we have the Java Virtual Machine (VM) with its c[r]

9.5.4 DEPTH TESTING
Depth testing is the final test in the OpenGL ES fragment pipeline. It is used for sorting the primitives at each pixel based on their distance from the camera. Typically we want the closest object to cover the ones farther away. However, some algorithms exist th[r]

12.2.5 PARAMETER PASSING
The parameter-passing semantics of Java are very easy to remember: int , float , and other primitive types are passed by value, everything else by reference. However, what happens to a referenced object is up to each method. It may be written to, its contents may be copied[r]

198 OPENGL ES RASTERIZATION AND FRAGMENT PROCESSING C H A P T E R 9
they do not have to be the same (for example 32 × 64 is a valid size). The two format parameters, internalformat and format , must be the same, and they must be one of the formats in the table below. The table also[r]

The flat shading model is somewhat awkward to use, and does not usually give the result one might expect as the lighting is calculated using only a single vertex and a single nor- mal per triangle. Even if the faceted look of a polygonal object is desired, you might well use smooth shading and[r]

glTexEnvi( GL_TEXTURE_ENV, GL_OPERAND2_RGB, GL_ONE_MINUS_SRC_ALPHA ); glTexEnvi( GL_TEXTURE_ENV, GL_OPERAND0_ALPHA, GL_SRC_ALPHA );
9.2.8 POINT SPRITE TEXTURING
Point sprites are another feature introduced in OpenGL ES 1.1. Many natural phenomena such as fire or smoke[r]

Performance tip: Do not confuse Sprite3D with point sprites in OpenGL ES. Because each instance of Sprite3D incorporates its own transformation, it is too slow for most use cases of point sprites. The scaling computations are also more complex than for point sprites. Part[r]

Regardless of the light type, you can set the light color through setColor
using the familiar hexadecimal 0xAARRGGBB color notation. For example,
myLight.setColor(0x00FF3311) gives myLight a strong red tint. The inten- sity of the light is set separately in floating point using the[r]

F i g u r e 15.1: Two variants of billboard trees. On the left, the trees are aligned with the Z axis of the camera; on the right, they are aligned to face the camera origin. In both cases, the vertical axis of each tree is constrained to be perpendicular to the ground plane.
Performance tip: Al[r]

14.1.4 EXAMPLE
Now we know how to build some geometry in M3G and draw it. Let us illustrate this with a more comprehensive example where we create some colored triangles and render them. We assume that you have set up your Graphics3D and Camera as described in Chapter 13; make sure[r]

pitfall: Your keyframe sequences are not valid until a valid duration is set. This concerns all sequences, regardless of whether they loop or not.
We mentioned looping sequences, and often you will use exactly those. For example, the motion of a helicopter rotor is easily defined using just[r]

298 BASIC M3G CONCEPTS C H A P T E R 13
a LUMINANCE_ALPHA image would consist of two bytes giving the luminance and alpha of the first pixel, followed by two bytes giving the luminance and alpha of the second pixel, and so on. The pixels are ordered top-down and left to right, i.e., the first widt[r]

object (see Section 13.2) instead of a Graphics .
So what exactly happens when you bind and then later release a target? From the developer’s point of view, nothing much: bindTarget simply flushes all 2D drawing commands so that 3D rendering can proceed, and releaseTarget does the opp[r]

not strictly true. The VertexArray and KeyframeSequence classes do in fact have special encodings as an option. However, the encodings are almost trivial.
Vertex arrays—including colors, normals, texture coordinates and vertex positions—can be compressed with delta encoding . This means that eac[r]

The point is the simplest OpenGL primitive, and it requires only one vertex. Its primary property is its size, which is set by the function
void glPointSize{fx} ( type size).
The point size corresponds to its diameter (the total width), defined in pixels, and it defaults to 1. Points can b[r]

The 2D coordinate system used in OpenGL (ES) has its origin at the lower left corner such that x grows to the right and y upward, as illustrated in Figure 2.14. In many windowing systems, as well as in M3G, the y axis is flipped: the origin is at the upper left corner and
y grows down[r]