Hit Mask Component

Overview

HitMask is designed to create decal effect on the character using one texture.

HitMask renders to a texture with UV coordinate of matching world location for skeletalmesh so that you can use that mask to filter - i.e. shot wounds or any other effect. When you give world location with parameter, it will find the matching UV coords and render white circles around the coordinate.

How to implement

This step describes how to implement this feature for your game.

Add Component to Actor

SceneCapture2DHitMaskComponent is the one responsible to render to texture. This component needs to attach to the pawn or skeletalmesh actor.

      // Add hit mask to the actor
      Begin Object Class=SceneCapture2DHitMaskComponent Name=HitMaskComp
      End Object
      HitMaskComponent=HitMaskComp
      Components.Add(HitMaskComp)

Create a texture per Actor

Unless you want all characters to share same texture, you'd probably like to create texture and give that as render target for Hit Mask Component.

    // Create Mask Texture of 64x64
      MaskTexture = class'TextureRenderTarget2D'.static.Create(64, 64, PF_G8, MakeLinearColor(0, 0, 0, 1));

      if ( MaskTexture!=none )
      {
            // Update HitMaskComponent with this texture
            HitMaskComponent.SetCaptureTargetTexture( MaskTexture );
      }

Add mask to the texture

This is to add one circle to the world location of MaskWorldLocation with size of Radius regardless normal test or not.

HitMaskComponent.SetCaptureParameters(MaskWorldLocation, Radius, MaskStartLocation, FALSE); // send capture parameter

MaskStartLocation isn't needed if you don't want any direction test to be done in shader. For example, if you'd like to create hit wounds on the character on the chest, you would not like to render mask behind of character where hit wouldn't have made although it's within the radius. MaskStartLocation indicates the origination point and last parameter TRUE will do hit normal test.

If FALSE, the normal test won't be done and it will just create sphere around the world location.

This is created to U unmirrored (V mirrored) since you don't want to create same thing in both places.

How to set it for your character

Now you have this texture to be used for your character material.

Texture Parameter

In your material, create texture parameter that can be replaced in game. That will be the target texture we're going to create.

Now you need to unmirror the texture. Since when we render it will unmirror U, make sure you do have texture sampling to Unmirror U as well.

Replace texture parameter in code

Now time to set the mask texture to the parameter, so that

      // get first parameter
      MIC = Mesh.CreateAndSetMaterialInstanceConstant(0); // material you'd like to replace
      if ( MIC != none &&  MaskTexture!=none )
      {
            // Set new texture as FilterMask parameter
            MIC.SetTextureParameterValue('FilterMask', MaskTexture); // use this texture to be used by your material
      }

Parameters

• MaterialIndex : Which material section to render?
• ForceLOD : If -1, use current LOD.
• HitMaskCullDistance : Cull distance. If further than this, it won't be tested

Fading related variable

You can have it fade out after a while. This is the tweak parameters.

• FadingStartTimeSinceHit : Fading start time after last hit. By default 10 seconds. If -1, it's infinite. If continuous hit comes in, it will stop fade.
• FadingPercentage : % of color to apply - Range of 0 to 1
• FadingDurationTime : Fading duration time since fading starts - in second
• FadingIntervalTime : Fading interval - in second

Limitation

This is cheap way to create decals on the character but it's limited in terms of shape you're creating. It's creating fading circle around the point. Also by default it unmirror U only. So if you have chacter that has mirroring V it can have duplicated mask on both side. It's easy to fix but you can waste memory if you don't use all sections.