# Explosion Lighting Unreal

Mostly explained in the video. Was inspired to try an idea on lighting fx explosions. I like how it turned out. next step is to get the rotation of the smoke object to be as I want them by rebuilding this in Niagara.

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It is nice to see some endeavors for visualizing light emission properties in particle volumes & meshes. The results are really neat!

Something else that could help bolster this further (even in a stylized effect), is to approximate how much your mesh / volume surface is displacing over time. By tracking the rate of change at a given point, you could map that to a velocity range that would represent heat & expansion. This way, you wouldnâ€™t have to try to guess a volume gradient by hand. It would also conform to the topology of your mesh surface (which is a big plus). You could then do some extra magic on top by isolating crevices and pumping the heat production up in those areas as well.

Here is a quick â€śvisualâ€ť example to hopefully help with the description.
Imagine the white line being the surface of your geometry (letâ€™s say a sphere). As heat is produced and the gas begins to expand, it pushes out (or in the case of the image â€śdownâ€ť) onto the surface of the geometry â€śthe white lineâ€ť. When this happens, the surface will begin to displace based on the rate of expansion per vertex based on the volume and gas characteristics â€śpushing againstâ€ť it.

Here is the code (paste it into a shadertoy shader) if you want to mess with it.
Please forgive the formattingâ€¦ and everything else, it is late and I donâ€™t know where I am or what I am doing

``````#define ASP_RATIO iResolution.x/iResolution.y
#define AMPLITUDE 0.3
#define FREQUENCY 4.0
#define OFFSET 0.0

float topologySurface(in float curve, in float p, in float width)
{
float lineObject = smoothstep(p-width, p+padding, curve)*
return lineObject;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
vec2 uv = fragCoord.xy/iResolution.xy;
vec2 uvRemap = vec2(((uv.x*2.0-1.0)*ASP_RATIO),
(uv.y*2.0-1.0));

float curve_a = uvRemap.y + (sin(uvRemap.x*FREQUENCY)*AMPLITUDE)+OFFSET;
float curve_b = uvRemap.y + (sin(uvRemap.x*FREQUENCY*1.250)*AMPLITUDE)+0.5;
float curve_c = uvRemap.y + (sin(uvRemap.x*FREQUENCY*1.80)*AMPLITUDE)-0.1;

float topology = (curve_a + curve_b + curve_c);
float fExpansionRate = smoothstep(((curve_a+curve_b+curve_c)/1.50/abs(uvRemap.y+0.4)),
((curve_a+curve_b+curve_c)*0.275), uv.y)*step(0.0,topology);

float surface = topologySurface(topology, -0.2, 0.1);
float surfaceForSlope = topologySurface(topology, -0.5, 0.1);
float s = dFdx(surfaceForSlope);
if (s<0.075){s = 0.0;}

vec3 surfaceColor = vec3(surface)*vec3(1.0, 1.0, 1.0);
vec3 fExpansionColor = mix(vec3(0.99, 0.2, 0.05),vec3(0.3, 0.872, 0.74), vec3(fExpansionRate))*fExpansionRate;
vec3 sColor = vec3(s)*vec3(5.0, 0.0, 1.0);
vec3 rFrame = surfaceColor + fExpansionColor + sColor;

fragColor = vec4(rFrame,1.0);
}``````
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Yeah I see what youâ€™re doing. Very cool, it gives me ideas on how to improve the system, altho Iâ€™d go about it in a more unreal shader graph way. Iâ€™ll have to test some ideas before I know what will help/make a noticeable difference. Thanks for the reply, this is great.

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amazingâ€¦i will try thisâ€¦ thnx for sharing â€¦

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