Mm... would be great if we could get a proper translation of the HDR section (and perhaps discussed elsewhere if we do).
MGS Tech Exposed (needs translation)
- Thread starter AlNom
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Mm... would be great if we could get a proper translation of the HDR section (and perhaps discussed elsewhere if we do).
I'm not sure my Japanese is up to technical translation, but I'll give it a try (feel free to pick this apart if your Japanese is better than mine 
):
The final HDR spec was decided after a number of experiments. Nowadays with up-to-date PC GPUs, HDR rendering just uses floating point buffer as it is efficient. However as the RSX was based on the GeForce 7800 GTX 2 generations ago, the fp buffer is not so efficient so alternatives were examined.
1) On RSX, FP16 buffer + MSAA is not available, and the jaggies were deemed unacceptable for the final image quality wanted for MGS4.
2) ARGB FP16 is 64 bit, so to do HDR with this with the 128 bit bus of the RSX is a fillrate hit. In addition, GeForce 6/7 alpha blending with FP16 is slow, it's better in RSX but still a bottleneck.
Result: ARGB 8 bit, using 32bit int buffer of 8888 was adopted until recently. Because HDR doesn't work with the int32 buffer, a device to store HDR was necessary.
In MGS4, the inverse of the brightness is stored. Specifically, it uses largest 3 bits of the RGB values, meaning 256 levels (8 bits) to express the inverse of the maximum luminance value.
When this value is close to 1.0, it's high precision, but the precision decreases as it tends to zero. 1.0 or less is usual LDR rendering.
As MGS4 has many dark scenes, maximum luminance of 1.0 or less is quite common, a brightness value of 0.25 is average. This would be quite low precision. So we tuned it so that 0.25 maps to a value of 1.0 in the inverse maximum luminance value.
The image captions:
http://game.watch.impress.co.jp/docs/20081203/3dmg415.htm
Unless HDR rendering is used, the shadow in the dark scene collapses
http://game.watch.impress.co.jp/docs/20081203/3dmg416.htm
If HDR rendering is used, the shadow inside the dark scene is visible, but it tends to make the outside scene dazzling. Because real sight works in the same way, it is more natural
http://game.watch.impress.co.jp/docs/20081203/3dmg417.htm
HDR rendering of the maximum luminance inverse number storage system which MGS4 uses. 0.25 is the average brightness
http://game.watch.impress.co.jp/docs/20081203/3dmg418.htm
Visualisation of the HDR encoding buffer
http://game.watch.impress.co.jp/docs/20081203/3dmg419.htm
Colour buffer after the tone map
):The final HDR spec was decided after a number of experiments. Nowadays with up-to-date PC GPUs, HDR rendering just uses floating point buffer as it is efficient. However as the RSX was based on the GeForce 7800 GTX 2 generations ago, the fp buffer is not so efficient so alternatives were examined.
1) On RSX, FP16 buffer + MSAA is not available, and the jaggies were deemed unacceptable for the final image quality wanted for MGS4.
2) ARGB FP16 is 64 bit, so to do HDR with this with the 128 bit bus of the RSX is a fillrate hit. In addition, GeForce 6/7 alpha blending with FP16 is slow, it's better in RSX but still a bottleneck.
Result: ARGB 8 bit, using 32bit int buffer of 8888 was adopted until recently. Because HDR doesn't work with the int32 buffer, a device to store HDR was necessary.
In MGS4, the inverse of the brightness is stored. Specifically, it uses largest 3 bits of the RGB values, meaning 256 levels (8 bits) to express the inverse of the maximum luminance value.
When this value is close to 1.0, it's high precision, but the precision decreases as it tends to zero. 1.0 or less is usual LDR rendering.
As MGS4 has many dark scenes, maximum luminance of 1.0 or less is quite common, a brightness value of 0.25 is average. This would be quite low precision. So we tuned it so that 0.25 maps to a value of 1.0 in the inverse maximum luminance value.
The image captions:
http://game.watch.impress.co.jp/docs/20081203/3dmg415.htm
Unless HDR rendering is used, the shadow in the dark scene collapses
http://game.watch.impress.co.jp/docs/20081203/3dmg416.htm
If HDR rendering is used, the shadow inside the dark scene is visible, but it tends to make the outside scene dazzling. Because real sight works in the same way, it is more natural
http://game.watch.impress.co.jp/docs/20081203/3dmg417.htm
HDR rendering of the maximum luminance inverse number storage system which MGS4 uses. 0.25 is the average brightness
http://game.watch.impress.co.jp/docs/20081203/3dmg418.htm
Visualisation of the HDR encoding buffer
http://game.watch.impress.co.jp/docs/20081203/3dmg419.htm
Colour buffer after the tone map
Once again japanese website gameimpress has posted a tech expose... humbly requesting a summary from anyone who can read it...
http://game.watch.impress.co.jp/docs/20081203/3dmg4.htm
http://game.watch.impress.co.jp/docs/20081203/3dmg4.htm
http://www.softimage.com/products/xsi/customer_stories/metal_gear_4/default.aspx
Might be the same or similar.
Might be the same or similar.
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