Using HDRI Environment Maps - casting sunlight on character

Naramatabench

I appreciate that there are many threads on this topic and I have read most of them without finding the answer to my question. I apologise in advance if this does appear somewhere and I missed that thread.

I am soaring up the Daz Studio learning curve after only a few weeks but I have still a long way to go. HDRI Environment Maps are causing me a headache. I have downloaded a number from HDRIHaven and have found that they come in two types - the first, and rarer, are ones that light the character in sunlight and move the sun as the Dome is rotated (Dome and Scene setting). The others do not highlight the character in sunlight irrespective of where I position her even in a sunny place in the Map; she is permanently in shadow. Rotating the Dome makes no difference to how the light falls on her. Also, there are no shadows off her. There are some that highlight her in sunslight which moves with Dome rotation but do not cast a shadow. What am I missing? I know that I can use Sun and Sky which I do like for the sunlight effects but I cannot get the same detail as a HDRI Map. 

Thanks for any advice.

Richard Haseltine

Are the problem maps much smaller than those that work? It may simply be that they lack sufficient range of values to give bright light and dark shadows.

AgitatedRiot

IS the draw ground turn on in the environment? Is the character on the Ground? I have found alot of HRDIS from that web site the ground doesn't sit right.

cajhin

First, it doesn't matter if you move the figure around, into or out of the 'shadows'. The HDRI dome is an illusion, which lights your figure depending on how bright the dome is. Shadows on the HDRI ground are an illusion too, there is no 'real' shadow since there is no object that blocks the light.

If the dome contains a mega-bright spot (sun) then you'll get highlights and shadows. If the dome is overcast, with a rather constant bright white sky, then you won't get shadows, as your figure is lighted evenly from all sides. Only way to get real highlights and shadows with such an HDRI is to add a spotlight to the scene.

Naramatabench

Thank you very much for your responses.

The HDRI Maps are all 4K and I have tried with the Draw Dome both ON and OFF. Curiously, the ones that work ie cast excellent shadows and the direction of the Sun moves with Dome rotation have excellent ground contact whether Auto or Manual. The ones where the character is always in shadow irrespective of Dome rotation and sunlight cast in the map, the ground is more difficult to get correct - no matter what I do they seem suspended in the air giving an unrealistic look. An excellent example of a Map that works brilliantly is "Spiaggia_di_Mondello". One that does not work (for me in this context) is "Topanga_Forest_B" both from HDRIHaven. 

Of course, this may be me and my learning curve not knowing what I am doing! Or is there a difference in the HDRI Maps.

Many thanks again.

 

cajhin

If you look at the hdri images, the brightest parts of the sky are both white. That's because your monitor cannot display more than 'white'.

A HDR (high dynamic range) can go much further, it can make the sun 1000x brighter than a white cloud, but your monitor cannot show this. Imagine wearing 6 sunglasses ("exposure -6 stops") and staring into the sky. The first image shows the difference between Spaggio di Mondello (I like that one too, btw), and your forest (which is from hdrlabs btw).

You will notice that only Spaggio has a sun. In the forest, the photographer put his tripod into the shadows and rotated the camera in all directions. He never filmed the sun, so the resulting HDRI has no sun - and in DS, your figure always looks like it's standing in the shadow, no matter how you shift the hdri around.

Best fix is to find another forest scene that was shot in sunlight. A crude fix is to just copy and paste a sun into the forest hdri (you'll need Affinity Photo or Photoshop to edit HDRs). I've attached a render how that looks.

 

Richard Haseltine

Naramatabench said:

Thank you very much for your responses.

The HDRI Maps are all 4K and I have tried with the Draw Dome both ON and OFF. Curiously, the ones that work ie cast excellent shadows and the direction of the Sun moves with Dome rotation have excellent ground contact whether Auto or Manual. The ones where the character is always in shadow irrespective of Dome rotation and sunlight cast in the map, the ground is more difficult to get correct - no matter what I do they seem suspended in the air giving an unrealistic look. An excellent example of a Map that works brilliantly is "Spiaggia_di_Mondello". One that does not work (for me in this context) is "Topanga_Forest_B" both from HDRIHaven. 

Of course, this may be me and my learning curve not knowing what I am doing! Or is there a difference in the HDRI Maps.

Many thanks again.

I meant file size rather than rsolution, as that can give an indication of how much variation in tone there is.

Naramatabench

Excellent advice once again - a real big help to beginners like me. So, it is down to how the HDRI was shot initially and thus how the Sun was employed in the photo (or not!). If it is used you get the dramatic sunlight effects of Spaggio. If not you don't. So for these effects it is a matter of finding the right HDRI. I'm familiar with Photoshop but would you mind explaining exactly what you mean by "copy and pasting a sun" into the HDRI? Your render is exactly the effect I'm looking for. 

Many thanks

cajhin

HdriHaven provides these helpful renders with the 4 balls. Notice how some of them throw hard, sharp shadows (clear sky, summer sun), while others barely have any shadows (overcast, invisible sun). You get about the same shadows in your renders, when you use those hdris.

To 'hack' the sun, I simply opened both Spaggio and the Forest in Affinity Photo (any editor that can deal with *.hdr files. Do *not* save as .jpg/png). Then I copied the sun in Spaggio (just a small piece of the photo), and pasted it into the forest hdri. Roughly where the real sun would be, so that the rendered shadows go into the same direction as the 'baked' shadows in the hdri. You can also vary the daytime, by putting your fake sun higher on the photo (noon) or lower (afternoon, more from the side).

The result can look quite ok, as long as the sun is outside of your camera viewport (you don't have to do a clean job with the copy&paste, if the sun is only a light source, but not directly visible)

Naramatabench

Excellent Cajhin, this has been a great help and much appreciated.

Naramatabench

So, I'm back with more questions on the same theme. I have spent some useful lockdown hours playing with these HDRI maps. I came across "Tropical Beach" in HDRLabs. It looks very similar to "Spiaggia" - an excellent beach with full sun. Yet "Spiaggia" casts excellent shadows and the characters can move around in the sunlight or shade depending on Dome Rotation. "Tropical Beach" also has a full sun but the characters are always in shadow. I fully understand the point about "Topanga" as noted above - although there is lots of dappled sunlight amongst the trees there is no "Sun" in the photo so no sun-lighting effect on the characters and no shadows. But this is not the case with "Tropical Beach". 

On a further point I tried placing spotlights in the scene to create a sunlight and shadow effect - good opportunity to learn about lighting. Except that I could not get them to give any light. Same setting "Dome and Scene", "Infinite" and "Draw Dome" on. Obviously another beginner's error but what am I doing wrong? I have yet to try the "Copy and Paste" Sun effect using PS. 

Once again, very many thanks in advance for your assistance.