Basic shader not rendering STL object correctly

beginners
#1

Hi,

I’m learning myself shaders using the tutorials form lighthouse3d website, I was using ofSphere for my examples, I had not problems at all, then I decided to test with a different 3d object, so I download a teapot from the grabcad website unfortunately the shader does not render the teapot the same way it renders a ofSphere, please see image attached as reference.

Here is my code
testApp.cpp

  
#include "testApp.h"  
  
void testApp::setup(){  
	ofSetVerticalSync(true);  
	  
	camera.setDistance(400);  
	  
	shader.load("shaders/shader.vert", "shaders/shader.frag");  
	  
	teapot.loadSTL(ofToDataPath("teapot.stl"));  
	teapot.scaleModel(5);  
//	teapot.centerModel();  
	  
	glEnable(GL_DEPTH_TEST);  
}  
  
void testApp::draw(){  
	ofBackground( ofColor::black );  
	ofEnableLighting();  
	  
	camera.begin();  
  
	shader.begin();  
	  
	float posX = ofGetMouseX() - ofGetWidth() * 0.5;  
	float posY = ofGetMouseY() - ofGetHeight() * 0.5;  
	ofVec3f lightPos(posX, -posY, 200);  
	lightPos.normalize();  
	shader.setUniform3fv("lightPos", lightPos.getPtr());  
	  
	ofSphere( 80, 0, 0, 30 );  
	  
	ofPushMatrix();  
	ofTranslate(-80, -20);  
	teapot.draw();  
	ofPopMatrix();  
	  
	shader.end();  
	  
	camera.end();  
}

shader.vert

  
varying vec3 normal;  
  
void main() {  
	normal = gl_NormalMatrix * gl_Normal;  
	  
	gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;  
}

shader.frag

  
uniform vec3 lightPos;  
varying vec3 normal;  
  
void main() {  
	float intensity;  
	  
	vec4 color;  
	  
	intensity = dot(lightPos, normalize(normal));  
	  
	if (intensity > 0.95) {  
		color = vec4(1.0, 0.5, 0.5, 1.0);  
	}  
	else if (intensity > 0.5) {  
		color = vec4(0.6, 0.3, 0.3, 1.0);  
	}  
	else if (intensity > 0.25) {  
		color = vec4(0.4, 0.2, 0.2, 1.0);  
	}  
	else {  
		color = vec4(0.2, 0.1, 0.1, 1.0);  
	}  
	gl_FragColor = color;  
}

Any help will be much appreciated!

shader-render-problem.jpg756×389

#2

Where can I download this teapot test this out? It almost looks like the vertices are oddly setup. Also, you only have 4 colors you’re spitting out, you probably want something more like this http://myheroics.wordpress.com/2009/07/09/glsl-blinn-phong-gouraud-shader/ no?

#3

Please find the file inf the link below, the reason for outputting just 4 colours is because I’m doing the lighthouse3d glsl tutorials, and the is the toon shader :wink:

https://dl.dropboxusercontent.com/u/26115638/OF-Share/teapot.stl

#4

Hey Nardove,

I see the model is scaled by x5, the normals are probably scaling as well in the stl draw. Have you tried glEnable(GL_NORMALIZE)?

#5

Hi Trent,

Did as suggested but same results, I even try not scaling the model and did not make any difference

#6

I’m assuming that you’re not happy with the jagged edges on the side of the teapot? That’s an artifact of the model afaict, here’s your shaders running with a different teapot. Is that the problem that you’re talking about?

![](http://forum.openframeworks.cc/uploads/default/2992/Screen Shot 2013-08-10 at 6.20.20 PM.png)

#7

Hi Josh,

I see, there most be something wrong with my implementation, the example I took it from uses the same teapot model that you have and it looks better, please have a look at -this link

#8

Hi Josh,

I see, there most be something wrong with my implementation but I cant see where :frowning: the example I took it from uses the same teapot model that you have and it looks better, please have a look at -this link

#9

Shouldn’t you be using:

  
  
	normal = gl_Normal;  
	gl_Position = ftransform();

since your light isn’t specified in eye space but is rather in world space (that’s the default in OF)

#10

Make the changes but unfortunately the same result

#11

Since you’re calculating your light in the shader, try not using ofLight. That calls a GL_Light, which I don’t think you need at all and might be messing things up. The light is really just a vector that you’re calculating and I wonder if that’s making things a bit strange at the moment.