google/filament

Spot light shows no shadow on invisible plane.

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#6,178 opened on Oct 12, 2022

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 (6 comments) (1 reaction) (1 assignee)C++ (2,178 forks)batch import
good first issue

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Description

I'm trying to use spot light to cast shadow on invisible plane but can't make it work. I found that directional light can cast shadow on both visible and invisible plane while spot light only shows shadow on visible plane.

directional light + lit plane Screenshot_20221012_171950_com example filamentcamera

directional light + unlit & shaderMultiplier plane Screenshot_20221012_172227_com example filamentcamera

spot light + lit plane Screenshot_20221012_175009_com example filamentcamera

spot light + unlit & shaderMultiplier plane Screenshot_20221012_174330_com example filamentcamera

material of invisible plane

material {
    name : shadow,
    shadingModel : unlit,
    shadowMultiplier : true,
    blending : transparent,
    transparency : twoPassesOneSide,
}
fragment {
    void material(inout MaterialInputs material) {
        prepareMaterial(material);
        material.baseColor = vec4(0.0, 0.0, 0.0, 0.5);
    }
}

Contributor guide

Research direction
Compare the shadow mapping implementation for spot lights and directional lights in Filament. Focus on the shadowMultiplier material path to identify why spot light fails to cast shadows on invisible shadow receiving planes.
Tech stack
cpp
Domain
None
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50