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I've implemented shadow mapping to generate shadows on a terrain. I render the scene (or the objects that cast shadows) from the light's perspective and then generate a depth map to be sampled during the second render pass (as all the tutorials on the web explain). It seemed to work fine but then I noticed that objects on a hill cast more than one shadow:

enter image description here

I think that's the correct behaviour since I don't render the terrain during depth map generation (the small quad on top right shows the depth buffer during the first render pass), so more terrain fragments look like they're behind the object from the light's point of view. No tutorial on shadow mapping seems to mention this issue though. Am I missing something or this shadow generation technique is very basic and issues like this one are likely to occur?

EDIT

here's my rendering code:

// in my Render() method:

    mShadowRenderer.SetLight(*mLights[0]);
    mShadowRenderer.Render();

    RenderSkyBox();
    RenderEntities();
    RenderGeometryTerrain(mTerrains[0], 
    mShadowRenderer.GetLightViewProjectionMatrix());

shadowRenderer is a class that is in charge of rendering to an off-screen buffer and to return a depth map as a shader resource view. The depth map is added to the terrain when I call the render method so it can be sampled in the terrai pixel shader to generate shadows.

Luca
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  • Some code would be very helpful. It's unclear exactly what technique you used to implement shadow mapping - the correct method would never give this behavior. – meowgoesthedog May 17 '18 at 18:29
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    If you don't draw the terrain to the depth map, then it is quite natural that you get a wrong result. Basically, the areas where you observe the wrong shadows would be shadowed by the terrain anyway. – Nico Schertler May 18 '18 at 16:32
  • @NicoSchertler Ok, that's the answer (or the confirm) I was looking for, please write a reply so I can accept it as a solution. – Luca May 31 '18 at 15:45

1 Answers1

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Also, the terrain needs to be rendered to the shadow map/dep map

Vertexwahn
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