• Capturing textures albedo

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    Building a Portable PBR Texture Scanner by Stephane Lb
    http://rtgfx.com/pbr-texture-scanner/

     

     

    How To Split Specular And Diffuse In Real Images, by John Hable
    http://filmicworlds.com/blog/how-to-split-specular-and-diffuse-in-real-images/

     

    Capturing albedo using a Spectralon
    https://www.activision.com/cdn/research/Real_World_Measurements_for_Call_of_Duty_Advanced_Warfare.pdf

    Real_World_Measurements_for_Call_of_Duty_Advanced_Warfare.pdf

    Spectralon is a teflon-based pressed powderthat comes closest to being a pure Lambertian diffuse material that reflects 100% of all light. If we take an HDR photograph of the Spectralon alongside the material to be measured, we can derive thediffuse albedo of that material.

     

    The process to capture diffuse reflectance is very similar to the one outlined by Hable.

     

    1. We put a linear polarizing filter in front of the camera lens and a second linear polarizing filterin front of a modeling light or a flash such that the two filters are oriented perpendicular to eachother, i.e. cross polarized.

     

    2. We place Spectralon close to and parallel with the material we are capturing and take brack-eted shots of the setup7. Typically, we’ll take nine photographs, from -4EV to +4EV in 1EVincrements.

     

    3. We convert the bracketed shots to a linear HDR image. We found that many HDR packagesdo not produce an HDR image in which the pixel values are linear. PTGui is an example of apackage which does generate a linear HDR image. At this point, because of the cross polarization,the image is one of surface diffuse response.

     

    4. We open the file in Photoshop and normalize the image by color picking the Spectralon, filling anew layer with that color and setting that layer to “Divide”. This sets the Spectralon to 1 in theimage. All other color values are relative to this so we can consider them as diffuse albedo.

  • sRGB vs REC709 – An introduction and FFmpeg implementations

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    1. Basic Comparison

    • What they are
      • sRGB: A standard “web”/computer-display RGB color space defined by IEC 61966-2-1. It’s used for most monitors, cameras, printers, and the vast majority of images on the Internet.
      • Rec. 709: An HD-video color space defined by ITU-R BT.709. It’s the go-to standard for HDTV broadcasts, Blu-ray discs, and professional video pipelines.
    • Why they exist
      • sRGB: Ensures consistent colors across different consumer devices (PCs, phones, webcams).
      • Rec. 709: Ensures consistent colors across video production and playback chains (cameras → editing → broadcast → TV).
    • What you’ll see
      • On your desktop or phone, images tagged sRGB will look “right” without extra tweaking.
      • On an HDTV or video-editing timeline, footage tagged Rec. 709 will display accurate contrast and hue on broadcast-grade monitors.

    2. Digging Deeper

    FeaturesRGBRec. 709
    White pointD65 (6504 K), same for bothD65 (6504 K)
    Primaries (x,y)R: (0.640, 0.330) G: (0.300, 0.600) B: (0.150, 0.060)R: (0.640, 0.330) G: (0.300, 0.600) B: (0.150, 0.060)
    Gamut sizeIdentical triangle on CIE 1931 chartIdentical to sRGB
    Gamma / transferPiecewise curve: approximate 2.2 with linear toePure power-law γ≈2.4 (often approximated as 2.2 in practice)
    Matrix coefficientsN/A (pure RGB usage)Y = 0.2126 R + 0.7152 G + 0.0722 B (Rec. 709 matrix)
    Typical bit-depth8-bit/channel (with 16-bit variants)8-bit/channel (10-bit for professional video)
    Usage metadataTagged as “sRGB” in image files (PNG, JPEG, etc.)Tagged as “bt709” in video containers (MP4, MOV)
    Color rangeFull-range RGB (0–255)Studio-range Y′CbCr (Y′ [16–235], Cb/Cr [16–240])


    Why the Small Differences Matter

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  • FXGuide – ACES 2.0 with ILM’s Alex Fry

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    https://draftdocs.acescentral.com/background/whats-new/

    ACES 2.0 is the second major release of the components that make up the ACES system. The most significant change is a new suite of rendering transforms whose design was informed by collected feedback and requests from users of ACES 1. The changes aim to improve the appearance of perceived artifacts and to complete previously unfinished components of the system, resulting in a more complete, robust, and consistent product.

    Highlights of the key changes in ACES 2.0 are as follows:

    • New output transforms, including:
      • A less aggressive tone scale
      • More intuitive controls to create custom outputs to non-standard displays
      • Robust gamut mapping to improve perceptual uniformity
      • Improved performance of the inverse transforms
    • Enhanced AMF specification
    • An updated specification for ACES Transform IDs
    • OpenEXR compression recommendations
    • Enhanced tools for generating Input Transforms and recommended procedures for characterizing prosumer cameras
    • Look Transform Library
    • Expanded documentation

    Rendering Transform

    The most substantial change in ACES 2.0 is a complete redesign of the rendering transform.

    ACES 2.0 was built as a unified system, rather than through piecemeal additions. Different deliverable outputs “match” better and making outputs to display setups other than the provided presets is intended to be user-driven. The rendering transforms are less likely to produce undesirable artifacts “out of the box”, which means less time can be spent fixing problematic images and more time making pictures look the way you want.

    Key design goals

    • Improve consistency of tone scale and provide an easy to use parameter to allow for outputs between preset dynamic ranges
    • Minimize hue skews across exposure range in a region of same hue
    • Unify for structural consistency across transform type
    • Easy to use parameters to create outputs other than the presets
    • Robust gamut mapping to improve harsh clipping artifacts
    • Fill extents of output code value cube (where appropriate and expected)
    • Invertible – not necessarily reversible, but Output > ACES > Output round-trip should be possible
    • Accomplish all of the above while maintaining an acceptable “out-of-the box” rendering

  • How are Energy and Matter the Same?

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    www.turnerpublishing.com/blog/detail/everything-is-energy-everything-is-one-everything-is-possible/

    www.universetoday.com/116615/how-are-energy-and-matter-the-same/

    As Einstein showed us, light and matter and just aspects of the same thing. Matter is just frozen light. And light is matter on the move. Albert Einstein’s most famous equation says that energy and matter are two sides of the same coin. How does one become the other?

    Relativity requires that the faster an object moves, the more mass it appears to have. This means that somehow part of the energy of the car’s motion appears to transform into mass. Hence the origin of Einstein’s equation. How does that happen? We don’t really know. We only know that it does.

    Matter is 99.999999999999 percent empty space. Not only do the atom and solid matter consist mainly of empty space, it is the same in outer space

    The quantum theory researchers discovered the answer: Not only do particles consist of energy, but so does the space between. This is the so-called zero-point energy. Therefore it is true: Everything consists of energy.

    Energy is the basis of material reality. Every type of particle is conceived of as a quantum vibration in a field: Electrons are vibrations in electron fields, protons vibrate in a proton field, and so on. Everything is energy, and everything is connected to everything else through fields.