Hdri in maya

Hdri in maya DEFAULT

VRayLightDome

Invisible ??Controls whether the shape of the VRayLight source is visible in the resulting render. When disabled, the source light is rendered in the current light color, otherwise, the light source itself is not visible in the scene.

The Invisible attribute only affects the visibility of the light when seen directly by the camera or through refractions. The visibility of the light with respect to reflections is controlled by the혻Affect Specular혻and혻Affect Reflections혻options.

Affect Diffuse혻??Determines whether the light is affecting the diffuse properties of the materials. With this option off, there will be no diffuse contribution from the light.

Affect Specular혻??Determines whether the light is affecting the specular of the materials (i.e. glossy reflections). With this option off, there will be no specular contribution from the light.

Affect Reflections혻??Determines whether the light will appear in reflections of materials, for both perfect and glossy reflections.

Affect Alpha혻??Determines whether or not the Dome Light is visible in the Alpha channel of the render. When enabled, you will have a white alpha where the background is visible. When disabled, you will have black alpha where the background is visible.

Diffuse contribution혻??A multiplier for the effect of the light's diffuse contribution on a surface.

Specular contribution혻??A multiplier for the effect of the light on the specular of the surface.

Sours: https://docs.chaosgroup.com/display/VMAYA/VRayLightDome

Ai Skydome Light

This simulates light from a sphere or dome above the scene, representing the sky. It can also be used with high dynamic range (HDR) images to perform image-based environment lighting. This is the node which is typically used for lighting exterior scenes. 

This light is designed for outdoor scenes and is represented by a spherical dome in the background. Importance sampling will trace rays to specific directions of this dome. However, in an interior scene, most of these rays will hit an object, getting no contribution from the light at all and thus creating noise. In this situation, adding light_portals to the windows will help to reduce noise in an interior scene when using the skydome_light.

When using Color Management in Maya (2017), HDR maps should be set to RAW. More information can be found here.

A tutorial that uses the skydome_light can be found here.

The lights page has more detail about the controls. The only additional attributes are:

Color

The color of the light. The skydome_light has a texturable color slot so that you can map a texture to be used for IBL.

Intensity

Intensity controls the brightness of light emitted by the light source by multiplying the color.

Resolution

The resolution controls the detail of reflections of the skydome. For most accurate results the Skydome light resolution must be set to match the HDRI image resolution, however, in many cases it can be set lower without a noticeable loss of detail in reflections. By default, the parameter is set to 1000. The higher the resolution parameter, the longer the skydome_light will take to precompute the importance tables for the light, which increases scene startup time.

The resolution attribute should be used with care. The higher the resolution value, the longer the skydome_light will take to pre-compute the importance tables for that light. For high-resolution maps, this can be very slow.

Format

The type of map being connected. It can be set to Lat-long (most common), Mirrored Ball or Angular.

Portal Mode

AOV Indirect

Visibility

Camera

By default, skydome lights are directly visible as a background. Lowering the influence of the light of camera rays makes them invisible to the camera, and makes the background transparent.

Transmission

Per-light scaling for transmission. Should be left at 1 to produce physically accurate results.

Diffuse / Specular / SSS / Volume

Per-light scaling for Camera, Transmission, Diffuse, Specular, SSS, Indirect and Volume. Weights scaling the light contribution to each of those components independently. Should be left at 1 to produce physically accurate results.

Only Area lights and Point lights (non-0 radius) are visible to the camera. Camera and Transmission values default to 0 with Area lights.

Sours: https://docs.arnoldrenderer.com/display/A5AFMUG/Ai+Skydome+Light
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You can use Final Gather to produce image-based lighting (or reflection) with a High Dynamic Range Image (HDRI). Image-based lighting takes the light (and light color) represented in an image you provide to illuminate the scene. An HDRI image has an extra floating point value associated with each pixel that is used to define the persistence of light at that point.

A high-dynamic range image is like several images with different exposures combined to show the full range of light (highlight and shadow). In fact, some HDR images are created by compositing several standard images of varying (bracketed) exposure in a special HDR application. This is required to simulate the wide range of available light in a single image -- an HDR image.

Tip:To understand the concept of High Dynamic Range (HDR) images, first think of a cathedral in which bright light spills in through an open door and illuminates part of the interior, except for some of the darker corners. If you were to enter the structure, your eyes would adjust to compensate for the excess or lack of light so that you can see properly.

HDR images have a greater capacity to describe light accurately (by way of floating point numbers) because they store the amount of light (rather than just color) represented in a pixel. This prevents 'blown out' or extremely dark areas in an image that your eyes compensate for in the natural world.

Using HDR images with Final Gather lets you provide extremely realistic lighting.

To use HDRI images as sources of light and reflection, see Image-based lighting (sky-like illumination).

Sours: https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/Maya/files/GUID-CB4649DA-DAA6-437B-9334-01080564020F-htm.html
Custom HDRI's for PhotoRealism - FULL WORKFLOW


This tutorial covers how to set up an HDRI image in Maya.

Set-up

Download this HDRI testing scene file.

Download the HDRI you intend to use (see chapter below).

Set the menu set to rendering.

Set the shelf to rendering.

HDRI

HDRIs let you light images using photographs. By using contrast information on an HDRI image, you can generate light based on it. Since the light would be from a photograph, renderings using HDRI images have a tendency to be more photo realistic.

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When an HDRI is created, the photographer takes pictures at different exposures of non-moving objects. Then, using software (Example: Adobe Photoshop), merges them all together into a 32 bit image which contains contrast information. You can create HDRIs yourself; basically you'll need a modern camera, a chrome ball, and some software package to merge them all together. The chrome ball is used to capure a spherical image of the enviromnent. Making an HDRI won't be covered in this tutorial.

There are two types of HDRI images used for lighting a digital scene: spherical and angular. Angular is the type that would be produced when using a chrome ball. Spherical HDRIs are more like panoramic images. Spherical HDRIs work the best.

If you don't intend to make your own HDRIs, you can buy them or get them free online.

Lists of free sites:
http://www.hdrmill.com/Freebies.htm

http://www.debevec.org/probes/

http://www.aversis.be/hdri/hdri-free.htm

http://hdri.3dweave.com/library/

http://en.wiki.mcneel.com/default.aspx/McNeel/BrianJames.html#HDRIs

Notes On Selecting Good HDRI Images

1. Look for HDRIs that have a direct light source.

2. The highest resolution HDRI might not always be the best. A lot of times it's just adding unnecessary render time. If you intend to use your HDRI as a background for your model or a large reflection, then resolution is important.

3. Purchased HDRIs have higher resolution and are better quality (not saying the free ones aren't any good).

4. Check the license on the HDRIs. A lot of the free ones are for non-commercial use. In other words, you can't use it to make profit.

5. Avoid HDRIs that have too much indirect light.

6. Avoid grainy HDRIs.

7. Chrome balls are the easiest HDRI to make, but they have less quality. So watch out for chrome balls that have specks of lint on them or dust.There's little you can do to clean this up. Also make sure the chrome ball was cropped correctly.

HDRIs In Maya

There are two ways of using an HDRI in Maya:

Using final gather and a sphere.

Using a mental ray IBL node.

Using Final Gather


Step one - Create a sphere. Scale it so it's larger than your scene.

Step two - Assign a surface shader material to it.

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Step three - Click on the checkerboard next to the out color to open the create render node window and create a file. This will connect the output of the file node to the input of the out color attribute.

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Step four - Beside image name, click on the folder icon and, when the file browser comes up, locate where you saved the HDRI image.

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Mental Ray

Mental Ray is needed to render HDRI images. Maya software and Maya hardware renders can't render them.

To load Mental Ray:

Step one - Go to window>settings/preferences>plug-in manager.

Step two - Roll down to the Mayatomr.mll; check loaded and auto load.

Step three - Go to window>render editors>render settings.

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Step four - Set the "render using" to mental ray.

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Now that we have mental ray loaded, we need to enable final gather.

Step one - On the common tab, roll down to render options and uncheck the "enable default light" option.

Step two - Go to the mental ray tab of the render settings.

Step three - Under secondary effects, check final gather.

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Step four - Roll down to the final gather tag and display it.

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Step five - The three most important attributes are accuracy and point density and scale. Increasing the accuracy will increase the render quality. Increasing the point density will increase the render quality, but can wash out the detail. Scale acts as a mulitplier for the final output from the final gather. A darker color will darken the rendering; a light tinted color will tint the rendering, etc.

Now for a test render.

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Tweaking The Rendering

Reselect your sphere and open the render settings for the shader.

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Step one - Click on the arrow beside the out color; this will take you to the file node with the HDRI image.

Step two - To change the contrast of the rendering, use the color gain attribute. If the rendering is underexposed, increase the value (V) to something like 2 or 3, etc.

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Using The IBL Node

The IBL node in mental ray lets you generate directional light from contrast information on the HDRI.

Step one - Repeat steps one through four in the mental ray section in the above chapter.

Step two - Go to the mental ray tab and roll down to the enviromnent tag.

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Step three - Click the create image based lighting button.

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As you can see it creates a sphere.This is where the HDRI will be projected.

Step four - Select it and open up the attribute editor (window>attributes editor).

Step five - Once again, click on the folder next to image name and, when the file browser opens, look up where you saved the HDRI image.

If your HDRI is a chrome ball HDRI, set the mapping to angular. If it's a paneramic style HDRI, set the mapping to spherical.

Step six - Roll down to the light emision tag.

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Step seven - Check emit light.

Step eight - The attributes quality U and V are the amount of directional light that will be created along the U and V coordinates of the image. For test rendering, the quality value of 150 each will work for most renderings. For the final rendering, depending on the HDRI resolution, I recommend a value of over 300.

Now you can render.

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Tweaking

Step one - If the rendering seems to be overblown or underexposed, in the mental ray IBL shapes attributes, check adjust light emmision color effects.

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Step two - Use the color gain attribute to adjust the exposure. If the rendering is underexposed, increase the value (V) to something like 2 or 3, etc.

Step three - To increase shadow quality, increase the ray depth limit.

Step four - The way the sampling system works is when mental ray is sampling the HDRI image, it won't sample all of it. It will try to sample the most important information. The sample attributes define how many times it will do this: more samples, better quality.

Low samples, according to the manual, should be set to 1\8th of the samples. Mental ray wil use this as the minimun sampling rate.

Final Gather Vs. IBL Node

In my personal experience I find that the IBL node is better suited for HDRI rendering. Final gather shadows are less realistic and there's less control. You can enable final gather when using an IBL node so you get the best of both worlds, butt he render time wil be noticably higher.

Conclusion

I hope this tutorial has taught you the fundamentals of using HDRIs in Maya.

Good luck.

Sours: http://www.3dtutorialzone.com/tutorial?id=70

In maya hdri

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Custom HDRI's for PhotoRealism - FULL WORKFLOW

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