[carpp]

Hi There. I'm using a HDR image to illuminate the Scene. Now i have some controls that says offset and scale to adjust it to the object. Now, when i use the scale factor the image is repeated on the sphere. How can i change the size and Position of the used sphere? When i activate the viewport view for the ibl sphere i just shows the mesh?

Any ideas?

[JDHill]

You cannot move the sphere; it must always remain centered on the camera's location. The sphere used in the viewport is there purely for the purpose of pre-visualizing the environment in Cinema; it is not actually exported to Maxwell.

[carpp]

ok. thanks! And what about size? will there be in future more control over the ibl sphere? Do i have more control in the studio app?

How can i position exactly a HDR sphere shot of a room to illuminate a car????

[JDHill]

Provided that you are using a proper HDRI (for Maxwell, you should use LatLong format -- rectangular, like a globe unwrapped), it doesn't make much sense to allow moving of the sphere. And if you cannot arbitrarily position the sphere, then it follows that there is also no reason to resize it; being centered on the camera, you could not perceive any difference between different sphere sizes. (and no, it works about the same in Studio as in the plugin)

If you are using an HDRI which was not made correctly, or is in the wrong format, then you could try building an environment manually; for example, create a sphere large enough to enclose your whole scene, ensure that its normals point inwards, and apply an HDRI emitter material to it. If your map is already not working correctly in Maxwell though, you may need to try using something other than a sphere to project the image.

[carpp]

it still remains unclear to me! Let´s play following scenario: I have three cars on top of each other and a hdri to illuminate. In the hdri there are some objects that will be reflected to the 3d object, like other cars, motorbike,...Now i zoom back the 3d object to see all the three cars...The Problem: now i have the wrong size relation between the seen objects in the hdri and the 3d object...the 3d object is now the same height like the car in the hdri...i can use a wide angle for the camera, but that can´t be the solution...

[JamesColeman]

I can see what you mean, but I think this is more of a Maxwell in general issue than a Cinema 4D specific issue. In fact, I think it's a render-engine-in-general issue because I'm struggling to think of examples of render engines where you can do what you're asking. Remember that an HDRI is created from photos taken from one specific point, and any object rendered using that HDRI will only have accurate reflections of that point. And with compositing it's always better to have a backplate, using an HDRI as a background will never be accurate because it's mapped to a sphere.

[carpp]

hi james. yes, i use a backplate for the composing. but it is very important to have real size reflections on the 3d object of all things that are in the hdri sphere!!

[JDHill]

Well, as James pointed out, the HDRI permanently encodes one specific environment as viewed from one particular point within that environment. In other words, the source of the difficulty is the HDRI itself.

Say that I created an HDRI using a mirror ball that was suspended two inches above the countertop in a small bathroom. Then I try to use this HDRI with your three stacked-up cars. An extreme example, but do you see the problem? This HDRI would only be good for making pictures of toothbrushes, or cars the size of Hot Wheels. If, by moving the HDRI projection sphere, I attempted to force the reflection of the bathroom faucet to appear at its correct 'real size', in comparison with these full-size cars, I'd find I couldn't do it, since that faucet is taking up, say, 30° of the field of view in the HDRI. As I attempted to move the perceived faucet further away from the cars by moving the HDRI projection sphere, I'd find that (a) the perspective of the faucet quickly becomes distorted, and (b) the camera ends up being outside of the sphere before the size of the faucet is even close to being comparatively correct.

In most cases, the situation will not likely be so extreme -- the HDRI will be close enough to make you feel that you could make it work by moving things around a little bit. That the result would be incorrect, though, is not a question; it is only a matter of degree. So as I wrote before, you can always try doing it manually using your own sphere and an HDRI emitter; maybe it will be close enough for your purposes.

[carpp]

That sounds pretty comprehensible! Thanks!

So, doing the a right sphere on location with let´s say a sigma 9mm and stitched together in ptgui and created als lang/long will be the best way and will fit on the standard size sphere from maxwell?

So i need to set the 3d objects to the right and real life size, right? That means in my case about 3 meters for a car. This will set the right size relation between the sphere and the 3d objects??? Or do i need to measure distances on location while doing the hdri sphere?

Should i leave the 3d objects with the coordinates 0-0-0 because this is the place from the hdri sphere was made? Moving the 3d object up and down or back and forth would be no good in terms of realistic reflections?

Do i expert the scene now as "cinema based units" or do set it to meter, or....


Many thanks for your support!

[macray]

you set the scene in whatever unit you prefer to model in, then via the plugin in the Cinema tab you just define what unit you used, or leave the cinema standard if you used the preset unit...