This property node defines a texture map and parameters for that map. This map is used to apply texture to subsequent shapes as they are rendered.

The node is similar to OIV.Inventor.Nodes.SoTexture2, but differs in the following significant ways:

1. It has no image field.

2. It doesn't load the texture image into system memory until the node is traversed. Depending on the scene graph, this may significantly reduce the use of system memory, e.g., if the scene has lots of LODs containing textures. On the other hand, when the scene graph is first traversed there may be a small delay while the textures are being loaded.

3. It has additional features (e.g., support for OpenGL paletted textures) for reducing the use of texture memory.

The texture is read from the file specified by the OIV.Inventor.Nodes.SoExtTexture2.filename field. There is no image field created. Data is sent directly to OpenGL.

The maximum system memory allowed for all OIV.Inventor.Nodes.SoExtTexture2 nodes (in total) can be set using OIV.Inventor.Nodes.SoExtTexture2.SetMemorySpace(System.Double).

If the memory allowed for texture images (OIV.Inventor.Nodes.SoExtTexture2.SetMemorySpace(System.Double)) would be exceeded by loading a new image, one or more existing images will be deleted from system memory. In most cases OpenGL texture objects will already have been created for the deleted images (i.e. OpenGL has a copy of the images), so this does not affect rendering.

If it is necessary to recreate an OpenGL texture object and the required texture image has been deleted from system memory, the node will automatically re-read the image file. For this reason, applications should be careful not to remove image files that might be needed during program execution.

To reduce the use of texture memory (by approximately a factor of 4), use the OIV.Inventor.Nodes.SoExtTexture2.UseTexturePalette(System.Boolean) method to request the image be converted to a 256-color paletted image. This feature is available only if the driver supports the GL_EXT_paletted_texture or GL_EXT_texture_color_table extension.

If the texture image's width or height is not a power of 2, and the Non Power Of Two (NPOT) extension is available on your graphics board, by default Open Inventor will send the image to OpenGL without modification. However, if the texture image's width or height is not a power of 2 (and the Non Power Of Two (NPOT) extension is not available on your graphics board), or the image's width or height is greater than the maximum supported by OpenGL, then the image will be automatically scaled up or down to the nearest power of 2 or the maximum texture size. For maximum speed, point-sampling is used to do the scaling. If you want higher quality scaling, pre-filter your images to a power of 2 smaller than the maximum texture size. Use the OpenGL glGetIntegerv(GL_MAX_TEXTURE_SIZE...) call to determine the maximum texture dimension for a specific OpenGL implementation. Setting the environment variable OIV_USE_NPOT to 0 will force the image to be rescaled (when necessary) even if the NPOT extension is available.

The quality of the texturing is affected by the textureQuality field of the OIV.Inventor.Nodes.SoComplexity node. The textureQuality field affects what kind of filtering is done to the texture when it must be minified or magnified. The mapping of a particular texture quality value to a particular OpenGL filtering technique is platform dependent, and varies based on the texturing performance. If mipmap filtering is required, mipmaps are automatically created using a simple box filter.

Performance Note: Automatic scaling of texture images to a power of 2 is a very convenient feature for prototyping, but it does take additional time the first time the texture node is traversed for rendering. For large images, or a large number of images, this can make the application seem slow while starting up or loading a new data file. Avoid this effect by either pre-scaling the image or by storing it as a sub-image in a "power of 2" image (then provide explicit texture coordinates such that only the sub-image is used).

FILE FORMAT/DEFAULT

ExtTexture2 {

filename	""
enableCompressedTexture	false
wrapS	REPEAT
wrapT	REPEAT
model	MODULATE
blendColor	0 0 0
loadingStatus	false
syncMode	SYNCHRONOUS
loadingMode	AUTO
loadingThreadPriorty	1
enableBorder	false
borderColor	0 0 0 0
maxAnisotropy	1.0
minFilter	AUTO
magFilter	AUTO
useAutoMipmap	false
internalFormat	AUTO_INTERNAL_FORMAT

}

ACTION BEHAVIOR

OIV.Inventor.Actions.SoGLRenderAction, OIV.Inventor.Actions.SoCallbackAction Sets current texture in state. Sets: OIV.Inventor.Elements.SoTextureImageElement

Reference