Using Dynamic Textures
To find out if the driver supports dynamic textures, check the D3DCAPS2_DYNAMICTEXTURES flag of the D3DCAPS9 structure.
Keep the following things in mind when working with dynamic textures.
- They cannot be managed. For example, their pool cannot be D3DPOOL_MANAGED.
- Dynamic textures can be locked, even if they are created in D3DPOOL_DEFAULT.
- D3DLOCK_DISCARD is a valid lock flag for dynamic textures.
It is a good idea to create only one dynamic texture per format and possibly per size. Dynamic mipmaps, cubes, and volumes are not recommended because of the additional overhead in locking every level. For mipmaps, D3DLOCK_DISCARD is allowed only on the top level. All levels are discarded by locking just the top level. This behavior is the same for volumes and cubes. For cubes, the top level and face 0 are locked.
The following pseudocode shows an example of using a dynamic texture.
DrawProceduralTexture(pTex)
{
// pTex should not be very small because overhead of
// calling driver every D3DLOCK_DISCARD will not
// justify the performance gain. Experimentation is encouraged.
pTex->Lock(D3DLOCK_DISCARD);
<Overwrite *entire* texture>
pTex->Unlock();
pDev->SetTexture();
pDev->DrawPrimitive();
}
| D3DUSAGE_DYNAMIC |
Set to indicate that the vertex buffer requires dynamic memory use. This is useful for drivers because it enables them to decide where to place the buffer. In general, static vertex buffers are placed in video memory and dynamic vertex buffers are placed in AGP memory. Note that there is no separate static use. If you do not specify D3DUSAGE_DYNAMIC, the vertex buffer is made static. D3DUSAGE_DYNAMIC is strictly enforced through the D3DLOCK_DISCARD and D3DLOCK_NOOVERWRITE locking flags. As a result, D3DLOCK_DISCARD and D3DLOCK_NOOVERWRITE are valid only on vertex buffers created with D3DUSAGE_DYNAMIC. They are not valid flags on static vertex buffers. For more information, see Managing Resources (Direct3D 9). For more information about using dynamic vertex buffers, see Performance Optimizations (Direct3D 9). D3DUSAGE_DYNAMIC and D3DPOOL_MANAGED are incompatible and should not be used together. See D3DPOOL. Textures can specify D3DUSAGE_DYNAMIC. However, managed textures cannot use D3DUSAGE_DYNAMIC. For more information about dynamic textures, see Using Dynamic Textures. |