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Member Since 18 Dec 2002
Offline Last Active Yesterday, 01:14 PM

Posts I've Made

In Topic: Trilinear texture filtering

Yesterday, 12:18 AM

The calculation of memory addresses for texture sampling is somewhat specialized logic. I wouldn't be surprised if even the latest GPU hardware had dedicated units for this specific purpose.


Conceptually, the operation finds the nearest texels of the sample vector(s), loads said texels, blends them based on their distance from the sample vector, and stores the result to shader-accessible registers. In practice, there is a bit more complexity than this smile.png


For selecting the mip levels to sample from, the sampler observes the partial derivatives ddx and ddy over the sample coordinate, and uses the length of the derivative vector [ddx, ddy] to determine the effective detail level of the current output pixel. Depending on the "sampling quality level" (as specified in control panel of some drivers), minimum, maximum or an arbitrarily biased value of [ddx, ddy] may also be used.


Additionally, when anisotropic filtering is enabled, the hardware considers the direction and maximum dimension of the derivative vector and takes n samples along it. This is done to get enough data for the sample, even though one of the sample coordinate derivatives might be considerably smaller than the other (in case the geometry slopes steeply wrt the screen space), and effectively improves the detail level of the texture in case the texture is not viewed exactly straight on.

In Topic: How to run a DX8 application on windows 7 64-bit

03 July 2015 - 10:57 PM

Find an old DirectX SDK which had VB6 support.

I believe that a suitable SDK was released around 2002-2004.

In Topic: How to run a DX8 application on windows 7 64-bit

03 July 2015 - 02:25 AM

VB6 and D3d interop was provided as a separate ActiveX dll. Said dll needs to be present in the target system.

I'm surprised that you can actually run the VB6 IDE itself in 64bit Windows, as it suffered significant compatibility issues the last time I tried it.

In Topic: Fading texture

01 July 2015 - 02:23 PM

If the fading is angle-dependent, it could be anisotropic filtering kicking in. How did you fix the mipmap issue?


EDIT: now that I took a look at the image, I believe you may have some z-buffer issues smile.png


That said, we can't be sure, since we have limited information available.

In Topic: Fading texture

30 June 2015 - 01:39 AM

You are probably not filling the mipmap chain of the texture.