NAME
SoTextureScalePolicy -
The SoTextureScalePolicy class is a node for controlling the texture
scale policy.
If a texture map is of size != 2^n, it must be scaled before OpenGL can
handle it. This node enables you to control how/if textures are scaled
before it is sent to OpenGL.
SYNOPSIS
#include <Inventor/nodes/SoTextureScalePolicy.h>
Inherits SoNode.
Public Types
enum Policy { USE_TEXTURE_QUALITY, SCALE_DOWN, SCALE_UP, FRACTURE }
Public Member Functions
SoTextureScalePolicy (void)
virtual void GLRender (SoGLRenderAction *action)
Static Public Member Functions
static void initClass (void)
Public Attributes
SoSFEnum policy
SoSFFloat quality
Protected Member Functions
virtual ~SoTextureScalePolicy ()
Detailed Description
The SoTextureScalePolicy class is a node for controlling the texture
scale policy.
If a texture map is of size != 2^n, it must be scaled before OpenGL can
handle it. This node enables you to control how/if textures are scaled
before it is sent to OpenGL.
Also, if a texture map is bigger than the maximum OpenGL texture size
(implementation and context dependent), it will be scaled down to the
maximum size. You can avoid this by setting the texture policy to
SoTextureScalePolicy::FRACTURE, in which case the texture will be split
into several small subtextures before the geometry using the texture is
rendered.
Setting SoTextureScalePolicy::policy to SoTextureScalePolicy::FRACTURE
will also cause the internal texture handling unit in Coin to
automatically downsample the individual subtextures to not use more
graphics card memory than necessary to cover the current screen size of
the texture.
These two aspects of SoTextureScalePolicy::FRACTURE rendering together,
subtexture fracturing and automatic downsampling, makes it possible to
have textures with almost unlimited size. The only real limit is the
amount of memory on the system, since the entire texture must fit into
CPU memory.
The SoTextureScalePolicy::FRACTURE policy is also very handy for using
the Coin library’s built-in handling of non-power-of-2 textures. This
will then be done completely transparent to the application programmer,
for maximum convenience. Below is a very simple example which
demonstrates how to use it. The texture has dimensions 3x3, but no
scaling (and thereby interpolation) will have to be done when
SoTextureScalePolicy::FRACTURE is specified:
#Inventor V2.1 ascii
Separator {
TextureScalePolicy { policy FRACTURE }
Complexity { textureQuality 0.01 } # don’t generate smoothed mipmaps
Texture2 {
image 3 3 4 # dimensions 3x3, RGBA (4-component) image
0xff0000ff 0x00ff00ff 0x0000ffff # red, green, blue
0xffff00ff 0xff00ffff 0x00ffffff # yellow, magenta, cyan
0x222222ff 0x777777ff 0xccccccff # dark, medium and light grey
}
Cube { }
}
.fi
Be aware that the triangle throughput is much slower when using the FRACTURE texture mode, since all triangles need to be clipped (using the CPU) against subtextures. It’s therefore usually not a good idea to use the FRACTURE mode on large triangle meshes.
Be aware that this class is an extension for Coin, and it is not available in the original SGI Open Inventor v2.1 API.
FILE FORMAT/DEFAULTS:
TextureScalePolicy {
policy USE_TEXTURE_QUALITY
quality 0.5
}
Since:
Coin 2.0
Member Enumeration Documentation
enum SoTextureScalePolicy::Policy Enumerates the available policy settings.
Enumerator:
USE_TEXTURE_QUALITY
Uses the texture quality to decide whether to scale up or down.
SCALE_DOWN
Always scales down.
SCALE_UP
Always scales up.
FRACTURE
Splits the texture into several subtextures, and clips the
geometry into each subtexture. Also automatically downsamples
the subtextures to not use more graphics card memory than
necessary versus the current screen size of the texture.
These two features makes it possible to have textures with almost
unlimited size. The only real limit is the amount of memory on the
system, since the entire texture must fit into CPU memory.
Be aware that the rendering is quite slow with this mode if the
texture(s) will be mapped onto lots of polygon primitives.
Constructor & Destructor Documentation
SoTextureScalePolicy::SoTextureScalePolicy (void) Constructor.
SoTextureScalePolicy::~SoTextureScalePolicy () [protected, virtual]
Destructor.
Member Function Documentation
void SoTextureScalePolicy::initClass (void) [static] Sets up initialization
for data common to all instances of this class, like submitting
necessary information to the Coin type system.
Reimplemented from SoNode.
void SoTextureScalePolicy::GLRender (SoGLRenderAction * action) [virtual]
Action method for the SoGLRenderAction.
This is called during rendering traversals. Nodes influencing the
rendering state in any way or who wants to throw geometry primitives at
OpenGL overrides this method.
Reimplemented from SoNode.
Member Data Documentation
SoSFEnum SoTextureScalePolicy::policy The policy setting. Default value is
USE_TEXTURE_QUALITY.
USE_TEXTURE_QUALITY means that SoComplexity::textureQuality will be
used to decide if the texture should be scaled up or down.
SoComplexity::textureQuality >= 0.7 means scale up, while < 0.7 means
scale down. Textures smaller than 256 pixels are never scaled down
since you lose too much information.
SoSFFloat SoTextureScalePolicy::quality The texture scale/resize quality.
Default value is 0.5.
This field can be used to force Coin to use a lower quality (but much
faster) image resize function. Currently, if you set this field to a
value < 0.5, a low quality resize function will be used, otherwise a
high quality (but slow) function will be used.
Author
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