The value in question should be the materialSpecularColor term. You might check this by simply removing the "+ materialSpecularColor * lightStrength * pow(cosAlpha, 10))" from the fragment shader.
The result may be too dark, so you have these options: - introduce an additional factor from 0.0 (no specular color) to 1.0 (current) to the term above - play with the lightStrength parameter (also affects the diffuse color part) - play with the lightColor parameter (also affects the ambient color part) HTH, and cheers Rainer On Tue, May 12, 2020 at 5:18 PM Tom O'Reilly <orei...@mbari.org> wrote: > I have little experience with OpenGL shader programs - can someone please > help me understand some GLSL shader code? > > I have source code for Qt 5.14.2, including DataVisualization, and would > like to modify the source to reduce specular “shininess” from Surface3D. This > screenshot > <https://drive.google.com/file/d/1Sx8d8guY1T13EkRaql5WVlMfowe1ai3j/view?usp=sharing> > shows a Surface3D that depicts topography, and it has a very “shiny” look > to it. Debugging with gdb I’ve determined that the following shaders are > generating this surface. Could someone please comment on how this shader > code affects the shininess of the surface? The code doesn't look like it's > directly based on the Phong reflection model, > <https://en.wikibooks.org/wiki/GLSL_Programming/GLUT/Specular_Highlights> > e.g. I don't see an exponential "shininess" term in the code. > > Thanks very much! > > *vertex shader (“shadow.vert”)* > > #version 120 > > uniform highp mat4 MVP; > > uniform highp mat4 V; > > uniform highp mat4 M; > > uniform highp mat4 itM; > > uniform highp mat4 depthMVP; > > uniform highp vec3 lightPosition_wrld; > > attribute highp vec3 vertexPosition_mdl; > > attribute highp vec3 vertexNormal_mdl; > > attribute highp vec2 vertexUV; > > varying highp vec2 UV; > > varying highp vec3 position_wrld; > > varying highp vec3 normal_cmr; > > varying highp vec3 eyeDirection_cmr; > > varying highp vec3 lightDirection_cmr; > > varying highp vec4 shadowCoord; > > varying highp vec2 coords_mdl; > > const highp mat4 bias = mat4(0.5, 0.0, 0.0, 0.0, > > 0.0, 0.5, 0.0, 0.0, > > 0.0, 0.0, 0.5, 0.0, > > 0.5, 0.5, 0.5, 1.0); > > void main() { > > gl_Position = MVP * vec4(vertexPosition_mdl, 1.0); > > coords_mdl = vertexPosition_mdl.xy; > > shadowCoord = bias * depthMVP * vec4(vertexPosition_mdl, 1.0); > > position_wrld = vec4(M * vec4(vertexPosition_mdl, 1.0)).xyz; > > vec3 vertexPosition_cmr = vec4(V * M * vec4(vertexPosition_mdl, > 1.0)).xyz; > > eyeDirection_cmr = vec3(0.0, 0.0, 0.0) - vertexPosition_cmr; > > lightDirection_cmr = vec4(V * vec4(lightPosition_wrld, 0.0)).xyz; > > normal_cmr = vec4(V * itM * vec4(vertexNormal_mdl, 0.0)).xyz; > > UV = vertexUV; > > } > > > > > *fragment shader (“surfaceShadowNoTex.frag”):* > > #version 120 > > varying highp vec2 coords_mdl; > > varying highp vec3 position_wrld; > > varying highp vec3 normal_cmr; > > varying highp vec3 eyeDirection_cmr; > > varying highp vec3 lightDirection_cmr; > > varying highp vec4 shadowCoord; > > uniform highp sampler2DShadow shadowMap; > > uniform sampler2D textureSampler; > > uniform highp vec3 lightPosition_wrld; > > uniform highp float lightStrength; > > uniform highp float ambientStrength; > > uniform highp float shadowQuality; > > uniform highp vec4 lightColor; > > uniform highp float gradMin; > > uniform highp float gradHeight; > > highp vec2 poissonDisk[16] = vec2[16](vec2(-0.94201624, -0.39906216), > > vec2(0.94558609, -0.76890725), > > vec2(-0.094184101, -0.92938870), > > vec2(0.34495938, 0.29387760), > > vec2(-0.91588581, 0.45771432), > > vec2(-0.81544232, -0.87912464), > > vec2(-0.38277543, 0.27676845), > > vec2(0.97484398, 0.75648379), > > vec2(0.44323325, -0.97511554), > > vec2(0.53742981, -0.47373420), > > vec2(-0.26496911, -0.41893023), > > vec2(0.79197514, 0.19090188), > > vec2(-0.24188840, 0.99706507), > > vec2(-0.81409955, 0.91437590), > > vec2(0.19984126, 0.78641367), > > vec2(0.14383161, -0.14100790)); > > void main() { > > highp vec2 gradientUV = vec2(0.0, gradMin + coords_mdl.y * gradHeight); > > highp vec3 materialDiffuseColor = texture2D(textureSampler, > gradientUV).xyz; > > highp vec3 materialAmbientColor = lightColor.rgb * ambientStrength > * > > materialDiffuseColor; > > highp vec3 materialSpecularColor = lightColor.rgb; > > highp vec3 n = normalize(normal_cmr); > > highp vec3 l = normalize(lightDirection_cmr); > > highp float cosTheta = clamp(dot(n, l), 0.0, 1.0); > > highp vec3 E = normalize(eyeDirection_cmr); > > highp vec3 R = reflect(-l, n); > > highp float cosAlpha = clamp(dot(E, R), 0.0, 1.0); > > highp float bias = 0.005 * tan(acos(cosTheta)); > > bias = clamp(bias, 0.001, 0.01); > > vec4 shadCoords = shadowCoord; > > shadCoords.z -= bias; > > highp float visibility = 0.6; > > for (int i = 0; i < 15; i++) { > > vec4 shadCoordsPD = shadCoords; > > shadCoordsPD.x += cos(poissonDisk[i].x) / shadowQuality; > > shadCoordsPD.y += sin(poissonDisk[i].y) / shadowQuality; > > visibility += 0.025 * shadow2DProj(shadowMap, shadCoordsPD).r; > > } > > gl_FragColor.rgb = > > (materialAmbientColor + > > materialDiffuseColor * lightStrength * cosTheta + > > materialSpecularColor * lightStrength * pow(cosAlpha, 10)); > > gl_FragColor.a = 1.0; > > gl_FragColor.rgb = visibility * clamp(gl_FragColor.rgb, 0.0, 1.0); > > } > > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > https://lists.qt-project.org/listinfo/interest > -- Software Engineer | Trimble Imaging Division Rotebühlstraße 81 | 70178 Stuttgart | Germany Office +49 711 22881 0 | Fax +49 711 22881 11 http://www.trimble.com/imaging/ | http://www.inpho.de/ Trimble Germany GmbH, Am Prime Parc 11, 65479 Raunheim Eingetragen beim Amtsgericht Darmstadt unter HRB 83893, Geschäftsführer: Rob Reeder, Jürgen Kesper
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