Problems with Hdr shadows

[Paulo Sampaio]

Hi all !

i downloaded a couple of .hdr and when i put it into scene, its going (i think) wrong, i dont know why but the shadows are being too much soft, i mean... really soft... and dont matter what high value I put into rays per FG Point, (tried some around 1200 to 2000) never reach a good definition, its all blur, and thats wierd because even i try put another hdri map, even a hdr desert file, with a point sun at the mid day, and the shadows still being very soft...

please, why this is happening? i understand some HDRI files should have soft shadows, but not too soft, even if i use another one, its still being soft, it look like 3dsmax actually is not taking the correct informations from HDRI files...



I dont know, already tried to disable the noise reduction system, check the gamma, change the fg rays, expousure control, i really dont know why...

What i can do to get the "correct" shadows? Please?

(sorry bad english)

[Zafar Iqbal]

It's not going to happen. You can tweak all you want - use whatever HDR image you want, but you won't get crisp shadows.

I'm just another artist and don't have the technical insight of how such things work. But neither FG, GI and IP will give you "shadows". IP is a bit better than FG, but far from what you are asking for.

The workaround is simple and easy - use a directional lightsource. Match it with the sun/main lightsource in your HDR and have it cast shadows. If you want a tiny bit of soft edge, which you often should have, then adjust the settings for that light type. If directional light can't produce soft shadows (I'm not familiar with 3ds) then use some other light type like a spotlight.

It's like this in all 3D apps.

[Paulo Sampaio]

Thank you! yeah your right i tried with Ip, but as you said Its far away from what I wanted, but the wierd thing is for example: if I load the same hdr in a software like hipershot it gives me perfect information of all HDR, the shadows are pretty nice. Well, anyway thank you so much.

[3DMadness]

You can try raise a lot the FG settings or use brute force (interpolation = 0) but I agree that it always lack a good IBL, vray is another render that can render HDR light much better.

[Ethan_Janssens]

you can't get sharp shadows out of HDR's... there is software that looks in the HDR and extracts the hightlight in this 360° dome (very likely the lightsource within this HDR, wether it's a sun, spotlight, ...)

an HDR as a lighting source is considered as a 360° LIGHTSOURCE in its own, with simple differences in peaks (lightsource of the HDR) and downs (shadows within the HDR)

these differences give a good overal lighting skeeme for a scene (if the HDR is actualy an HDR and not some 360° 8bit jpg converted to a HDR - that's cheating and the 32bit color range wouldn't be magicaly be filled in with new lighting information coming from an 8 of 16bit)

anyway, crips shadows are when a sun is shining without clouds for example. Clouds act like a dispertion of the light which gives softer shadows.

try this: in photoshop make a black image with a fat white dot in the center top and use this as a lightsource instead of the 32bitHDR you where using

this is practicaly the furtherst you can go considering everything is black in the 360° lightsource-dome, exept for the white dot which will act as a "sun"

these shadows from this source are not even sharp yet...

thats why when working with HDR's you add lights to the scene to match the HDR-environment you're trying to place the object in and you tweak the shadows in that asset-lightsource to match the ones in the HDR

hdr's are great to get fast global illumination calculations like final gather (cause they enlight a scene from 360° around) but are in no way fit for generating sharp shadows...

at HDR-labs http://www.hdrlabs.com/ they're constantly updating the software coming out for HDR's and stuff, there's some good software able to read an HDR, locate the light-source in that HDR and create an asset-light duplicating that HDR-lightsource for your scene

unfortunately thats better tweaked for VRay then Mental Ray - i think last time I checked for Mental Ray they create a "direct-light" lighting source... I'd prefer to see a generated mr_daylight-system... direct lighting isn't really matching my workflow with the photometric lights, but it could help with for example locating the light source so I can use the direct light to replace my daylight system with it...

dunno just thinking out loud

regards

[matthew999]

there is intresting post here

http://forum.mentalimages.com/showthread.php?t=5717

new feature not sures it implemented officially yet.. probably cause it increase render times too much, but allows much more accurate reading or hdri for sharp shadows

[Paulo Sampaio]

you can't get sharp shadows out of HDR's... there is software that looks in the HDR and extracts the hightlight in this 360° dome (very likely the lightsource within this HDR, wether it's a sun, spotlight, ...)

an HDR as a lighting source is considered as a 360° LIGHTSOURCE in its own, with simple differences in peaks (lightsource of the HDR) and downs (shadows within the HDR)

these differences give a good overal lighting skeeme for a scene (if the HDR is actualy an HDR and not some 360° 8bit jpg converted to a HDR - that's cheating and the 32bit color range wouldn't be magicaly be filled in with new lighting information coming from an 8 of 16bit)

anyway, crips shadows are when a sun is shining without clouds for example. Clouds act like a dispertion of the light which gives softer shadows.

try this: in photoshop make a black image with a fat white dot in the center top and use this as a lightsource instead of the 32bitHDR you where using

this is practicaly the furtherst you can go considering everything is black in the 360° lightsource-dome, exept for the white dot which will act as a "sun"

these shadows from this source are not even sharp yet...

thats why when working with HDR's you add lights to the scene to match the HDR-environment you're trying to place the object in and you tweak the shadows in that asset-lightsource to match the ones in the HDR

hdr's are great to get fast global illumination calculations like final gather (cause they enlight a scene from 360° around) but are in no way fit for generating sharp shadows...

at HDR-labs http://www.hdrlabs.com/ they're constantly updating the software coming out for HDR's and stuff, there's some good software able to read an HDR, locate the light-source in that HDR and create an asset-light duplicating that HDR-lightsource for your scene

unfortunately thats better tweaked for VRay then Mental Ray - i think last time I checked for Mental Ray they create a "direct-light" lighting source... I'd prefer to see a generated mr_daylight-system... direct lighting isn't really matching my workflow with the photometric lights, but it could help with for example locating the light source so I can use the direct light to replace my daylight system with it...

dunno just thinking out loud

Regards

Thank Very much... its totally clear now.

Thanks everybody for trying to help!