|
|
|
|
| |
Using the stencil buffer on the ATI
Rage128 and Rage128 Pro with Direct3D
|
|
|
The R128DX7StenFX sample program shows how the stencil buffer may be used to dissolve from one frame into another using different dissolve patterns. Three different dissolve patterns are demonstrated: random noise, a tiled pattern, and a plasma image. Figure 1 shows R128DX7StenFX doing a dissolve using the plasma pattern.
R128DX7StenFX demonstrates two ways to perform the dissolve. The first is to only draw the second frame inside the dissolve loop, slowly building it up over the first frame with each iteration of the loop. The second draws both the initial and final frames within the dissolve loop, setting complementary stencil compare functions for each. The former is faster, but can produce inaccurate results under certain circumstances. For example, if the dissolve pattern is changed part way through the dissolve sequence, artifacts from the former pattern will appear during the rest of the dissolve. In the file R128DX7StenFX.cpp, the DRAW_SECOND_FRAME_ONLY macro causes the first dissolve method to be executed. Disable this macro to perform the second dissolve method.
| |
|
 |
Figure 1
|
| |
|
R128DX7StenFX works as follows:
- If DRAW_SECOND_FRAME_ONLY is defined:
-
- Fill the stencil buffer with the desired dissolve
pattern.
- Set the stencil buffer to keep existing values
on stencil pass.
- Set the stencil function to D3DCMP_ALWAYS and
draw the first frame.
- Set the stencil function to D3DCMP_GREATEREQUAL
before starting the dissolve sequence.
- Dissolve sequence: loop from 0 to 255 in the
desired step.
- During each loop iteration, set the stencil
reference to the loop counter, draw the second
frame, and swap the drawing buffers.
- If DRAW_SECOND_FRAME_ONLY is not defined:
-
- Fill the stencil buffer with the desired dissolve
pattern.
- Set the stencil buffer to keep existing values
on stencil pass.
- Dissolve sequence: loop from 0 to 255 in the
desired step.
- At the start of each loop iteration, set the
stencil reference to the loop counter.
- Set the stencil function to D3DCMP_LESS and
draw the first still frame.
- Set the stencil function to D3DCMP_GREATEREQUAL
and draw the second still frame.
- Swap the front and back buffers. NOTE: Do NOT
clear the stencil buffer at the start of each
new frame.
- R128DX7StenFX Controls
-
- F1 - About
- F2 - Select Driver/Device/Mode
- [ALT]+[ENTER] - Toggle fullscreen/windowed
- [ENTER] - Toggle Go/Stop
- Space Bar - Single Step
- D - Initiate scene dissolve
- C - Cycle through dissolve patterns
- [ESC] - Quit
Downloads
DirectX 7 project file, source, executable, and support files
|
| |
 |
|
|
|
