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POhow to get a spotlight in opengl?
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copied!<p>reference <a href="http://www.chai3d.org/doc/classc_light.html" rel="nofollow noreferrer">http://www.chai3d.org/doc/classc_light.html</a></p> <p>code</p> <pre><code> light2->setPos(cVector3d( 0, 0,0.0)); // position the light source light2->m_ambient.set(0.8, 0.8, 0.8); light2->m_diffuse.set(0.8, 0.8, 0.8); light2->m_specular.set(0.8, 0.8, 0.8); light2->setDirectionalLight(false);//make a positional light </code></pre> <p>the rendering code which uses opengl is</p> <pre><code>void cLight::renderLightSource() { // check if light source enabled if (m_enabled == false) { // disable OpenGL light source glDisable(m_glLightNumber); return; } computeGlobalCurrentObjectOnly(); // enable this light in OpenGL glEnable(m_glLightNumber); // set lighting components glLightfv(m_glLightNumber, GL_AMBIENT, m_ambient.pColor()); glLightfv(m_glLightNumber, GL_DIFFUSE, m_diffuse.pColor() ); glLightfv(m_glLightNumber, GL_SPECULAR, m_specular.pColor()); // position the light source in (global) space (because we're not // _rendered_ as part of the scene graph) float position[4]; position[0] = (float)m_globalPos.x; position[1] = (float)m_globalPos.y; position[2] = (float)m_globalPos.z; //position[0] = (float)m_localPos.x; //position[1] = (float)m_localPos.y; //position[2] = (float)m_localPos.z; // Directional light source... if (m_directionalLight) position[3] = 0.0f; // Positional light source... else position[3] = 1.0f; glLightfv(m_glLightNumber, GL_POSITION, (const float *)&position); // set cutoff angle glLightf(m_glLightNumber, GL_SPOT_CUTOFF, m_cutOffAngle); // set the direction of my light beam, if I'm a _positional_ spotlight if (m_directionalLight == false) { cVector3d dir = m_globalRot.getCol0(); float direction[4]; direction[0] = (float)dir.x; direction[1] = (float)dir.y; direction[2] = (float)dir.z; direction[3] = 0.0f; glLightfv(m_glLightNumber, GL_SPOT_DIRECTION, (const float *)&direction); } // set attenuation factors glLightf(m_glLightNumber, GL_CONSTANT_ATTENUATION, m_attConstant); glLightf(m_glLightNumber, GL_LINEAR_ATTENUATION, m_attLinear); glLightf(m_glLightNumber, GL_QUADRATIC_ATTENUATION, m_attQuadratic); // set exponent factor glLightf(m_glLightNumber, GL_SPOT_EXPONENT, m_spotExponent); } </code></pre> <p>why do I get my whole environment uniformly lighted? how do I get a concetrated light around the origin 0,0,0, which fades away after 1 or 2 unit distance? My origin is the middle cube in the grid.<img src="https://i.stack.imgur.com/vS3Dh.png" alt="enter image description here"></p>

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