Z-fighting / dept buffer glitches in equidistant mode

[johanjohan]

Hi @hiroMTB , thank you for this very usable addon. I realize some depthbuffer glitches in TRIANGLE_SHADER mode when I draw ofBoxPrimitives for testing. Could you recommend a method to get rid of these glitches? So far I was only trying wth near/far clipping planes with no change at all.

I use
glEnable(GL_DEPTH_TEST);
glClear(GL_DEPTH_BUFFER_BIT);
glDepthFunc(GL_LESS);

BTW it works on windows10 OF 0.11.0

[hiroMTB]

Hello, thank you for yojr feedback!
Can you share example image?

[johanjohan]

sure!

[hiroMTB]

Why do you do glClear(GL_DEPTH_BUFFER_BIT)?

[johanjohan]

glClear(GL_DEPTH_BUFFER_BIT) is part of the attempts to improve on the z-fighting. the result is identical without. I can comment it out without change

[hiroMTB]

I tested by drawing cubes and it works ok. But when I inserted your 3 lines, I got glitches like yours. But I tested on macOS. Could you please post your code?

…

On Sat, Feb 15, 2020, 2:20 PM Michael Saup ***@***.***> wrote: glClear(GL_DEPTH_BUFFER_BIT) is part of the attempts to improve on the z-fighting. the result is identical without. I can comment it out without change — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1?email_source=notifications&email_token=AABPGABJHNTPD4HE2WPJBJLRC7T2RA5CNFSM4KVO4RD2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEL3KMXQ#issuecomment-586589790>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABPGAAXE5YNSL2WP4AHRRDRC7T2RANCNFSM4KVO4RDQ> .

[johanjohan]

strange...I only added the 3 lines after seeing the glitches, i see no difference in windows10

.h file almost identical

#pragma once

#include "ofMain.h"
#include "ofxEquidistantProjection.h"
#include "ofxGui.h"

using namespace ofxequidistantprojection;
using namespace glm;

class ofApp: public ofBaseApp{
	public:
		void setup();
		void update();
		void draw();
		void keyPressed(int key);
		
        void begin(ShaderType type);
        void end(ShaderType type);
        
        ofxEquidistantProjection proj;
    
        ofSpherePrimitive sphere;
        ofEasyCam normalCam;
    
        ofxPanel gui;
        ofxLabel fps;
        ofParameterGroup prm;
        ofParameter<bool> bEqui;
        ofParameter<bool> bDraw2dGuide;
        ofParameter<bool> bDraw3dGuide;
        ofParameter<bool> bDrawPoints;
        ofParameter<bool> bDrawLines;
        ofParameter<bool> bDrawTriangles;
    
        ofParameter<glm::vec3> objPos;
        ofParameter<float> objScale;
        
        ofVboMesh vboPoints;
        ofVboMesh vboLines;

		const static int windowSize;

};

.cpp

#include "ofApp.h"

using namespace glm;

const int ofApp::windowSize = 1024;


struct Obj {

	glm::vec3		p;
	ofColor			c;
	float			s;
	ofBoxPrimitive	box;

	Obj() : p(0, 0, 0), c(ofColor::red), s(1) {
		box.setUseVbo(true);
	}

	void randomizePosSize() {
		s = ofRandom(0.1, 1.0);

		const float d = 7.0 / 3; // 7.0
		p = glm::vec3(
			ofRandom(-d, +d),
			ofRandom(-d, +d),
			ofRandom(-d, +d)
		);
		box.set(s, s, s);
		box.setPosition(p);
	}

	void addColors(const ofColor &_c) {
		vector<vec3> & vs = box.getMesh().getVertices();
		for (int i = 0; i < vs.size(); i++) {
			box.getMesh().addColor(_c);
		}
		box.enableColors();
	}

	void update(const float &_e11) {
		const float d = 3.0;
		box.setPosition(
			p + glm::vec3(
				ofMap(_e11, -1, +1, -d, +d),
				ofMap(_e11, -1, +1, -d, +d),
				ofMap(_e11, -1, +1, -d, +d)
			)
		);
	}
};
vector<Obj> objects;
const size_t numObjs = 100;


void ofApp::setup() {
	ofBackground(0);
	ofSetColor(255);
	ofSetCircleResolution(50);
	ofSetFrameRate(2000);
	ofSetVerticalSync(false);
	ofSeedRandom(123);

	proj.setup();
	proj.getCamera().setPosition(0, 0, 0);
	proj.getCamera().setNearClip(0.01); // 0.01 no change...
	proj.getCamera().setFarClip(1000); // 1000

	normalCam.setNearClip(0.01); // 0.01
	normalCam.setFarClip(1000);
	normalCam.setDistance(10);
	//normalCam.disableMouseInput();

	gui.setup();
	prm.add(bEqui.set("Equidistant Projection", true));
	prm.add(bDraw2dGuide.set("Draw 2D Guide", false));
	prm.add(bDraw3dGuide.set("Draw 3D Guide", false));
	prm.add(bDrawPoints.set("Draw Points", false));
	prm.add(bDrawLines.set("Draw Lines", false));
	prm.add(bDrawTriangles.set("Draw Triangles", true));

	prm.add(objPos.set("Object Position", vec3(0, 0, 0), vec3(-200, -200, -20), vec3(200, 200, 20)));
	prm.add(objScale.set("Object Scale", 1, 0, 10.0));
	gui.add(fps.setup("fps", "0"));
	gui.add(prm);

	vboPoints.setMode(OF_PRIMITIVE_POINTS);
	for (int i = 0; i < 100; i++) {
		vboPoints.addColor(ofColor(255, 255, 255));
		vboPoints.addVertex(vec3(ofRandom(-2, 2), ofRandom(-2, 2), ofRandom(-2, 2)));
	}

	vboLines.setMode(OF_PRIMITIVE_LINES);
	for (int i = 0; i < 100; i++) {
		vboLines.addColor(ofColor(255, 255, 255));
		vboLines.addVertex(vec3(ofRandom(-2, 2), ofRandom(-2, 2), ofRandom(-2, 2)));
	}

	sphere.setUseVbo(true); // ????
	sphere.setRadius(10);
	sphere.setResolution(10); // 10
	sphere.setPosition(0, 0, 0);
	sphere.setOrientation(ofVec3f(90, 0, 0));
	vector<vec3> & vs = sphere.getMesh().getVertices();

#if 0
	for (int i = 0; i < vs.size(); i++) {
		sphere.getMesh().addColor(ofFloatColor(1, 1, 1, 1));
	}
#else
	// 3j
	for (int i = 0; i < vs.size(); i++) {
		float angle = ofMap(i, 0, vs.size() - 1, 0, 270);
		ofColor col = ofColor::red;
		col.setHueAngle(angle);
		sphere.getMesh().addColor(col);
	}
#endif

	// 3j
	for (int i = 0; i < numObjs; i++) {
		Obj tmp;
		tmp.c = ofColor::red;
		tmp.c.setHueAngle(ofMap(i, 0, numObjs - 1, 0, 270));
		tmp.randomizePosSize();
		tmp.addColors(tmp.c);
		objects.push_back(tmp);
	}

	//GLint depthBits;
	//glGetIntegerv(GL_DEPTH_BITS, &depthBits);
	//ofLogNotice(__FUNCTION__) << "depthBits: " << depthBits;
}

void ofApp::update() {
	fps = ofToString(ofGetFrameRate());

	for (int i = 0; i < objects.size(); i++) {
		objects[i].update(
			sinf(ofGetElapsedTimef() / (i + 1) / (objects.size() / 44.f) )
		); 
	}
}

void ofApp::begin(ShaderType type) {
	ofPushMatrix();
	bEqui ? proj.begin(type) : normalCam.begin();
	ofDrawAxis(10);
	ofTranslate(objPos);
	ofScale(objScale, objScale, objScale);
}

void ofApp::end(ShaderType type) {
	bEqui ? proj.end(type) : normalCam.end();
	ofPopMatrix();
}

void ofApp::draw() {

	ofBackground(150);

	if (bDrawPoints) {
		glPointSize(3);
		begin(ShaderType::POINT_SHADER);
		ofSetColor(255);
		glColor4f(255, 255, 255, 255);
		vboPoints.draw();
		sphere.getMesh().setMode(OF_PRIMITIVE_POINTS);
		sphere.draw(OF_MESH_POINTS);
		end(ShaderType::POINT_SHADER);
	}

	if (bDrawLines) {
		begin(ShaderType::LINE_SHADER);
		ofSetColor(255);
		vboLines.draw();

		if (bDraw3dGuide) {
			ofNoFill();
			ofSetColor(0, 0, 255);
			proj.drawEquidistantHemisphere(10);
		}
		end(ShaderType::LINE_SHADER);
	}

	if (bDrawTriangles) {
		begin(ShaderType::TRIANGLE_SHADER);
		ofSetColor(255);
		sphere.getMesh().setMode(OF_PRIMITIVE_TRIANGLES);
		sphere.drawWireframe();
		end(ShaderType::TRIANGLE_SHADER);
	}


	if (bDraw2dGuide) {
		ofPushMatrix();
		ofSetupScreenOrtho();
		ofTranslate(ofGetWidth() / 2, ofGetHeight() / 2);
		ofSetColor(0, 255, 0);
		ofNoFill();
		proj.draw2dCircles(ofGetWidth() / 2);
		ofPopMatrix();
	}

	// https://learnopengl.com/Advanced-OpenGL/Depth-testing
	// some Z-fighting
	if (true)
	{
		const ShaderType shadertype = ShaderType::TRIANGLE_SHADER; // TRIANGLE_SHADER
		glEnable(GL_DEPTH_TEST);
		//glDepthFunc(GL_LESS);
		//glClear(GL_DEPTH_BUFFER_BIT);
		begin(shadertype);
		//ofEnableDepthTest();
		for (int i = 0; i < objects.size(); i++) {
			objects[i].box.draw(); 
		}
		end(shadertype);
	}


	ofSetupScreenOrtho();
	ofDisableDepthTest();
	gui.draw();
}


void ofApp::keyPressed(int key) {

	if (key == 's'){
		ofSaveScreen("_snaps/" + ofGetTimestampString() + ".png");
	}
}

main

#include "ofApp.h"

int main(){
	
	ofGLFWWindowSettings settings;
	settings.multiMonitorFullScreen = true;
	settings.setGLVersion(3,2);
    settings.setSize(ofApp::windowSize, ofApp::windowSize);
	//settings.setPosition(vec2(0,-1080));
	settings.setPosition(vec2(0,0));
	ofCreateWindow(settings);
    
	// this kicks off the running of my app
	// can be OF_WINDOW or OF_FULLSCREEN
	// pass in width and height too:
	ofRunApp(new ofApp());
}

lots of glitches, all looking good in normal camera mode

[hiroMTB]

Thanks!
I'm seeing the same issue on macOS.
And I can fix by commenting out glEnable(GL_DEPTH_TEST)
Hope it works on Windows too.

[johanjohan]

@hiroMTB yes, this works, but then the depth order is not correctly displayed, which is an issue for my case. I guess, the only solution will be to z-sort all objects before drawing, do you agree? Still, would have been so much better and probably faster to fix that in the shader if possible.
btw, your addon is very useful, fast and good quality. Thank you.

[hiroMTB]

I see.
In the triangle shader, I populated additional triangles in order to increase precision.
But I didnt calculate gl_Normal for each triangle. This might be the issue.

Here is the code.
https://github.com/hiroMTB/ofxEquidistantProjection/blob/master/example/bin/data/shadersGL3/tri.geom

You can see that GenerateTriangle() is called 4 times at the bottom. It means splitting the original triangle to 4 smaller triangles (subdivide). It might be okay to copy original normal and use for 4 subdivided triangles. But probably we need to apply equidistant projection to normal calculation too. It must be not so difficult. I think we can calculate like following way.

1. calculate starting point of normal (center of subdivided triangle)
2. calculate end point of normal (center + original normal)
3. apply equidistant conversion to 1 and 2. Result 1' and 2'
4. 2' - 1' = new normal

I'm not sure. It might be completely different reason.

[johanjohan]

@hiroMTB thank you. Are you going to give your fix-suggestion a try?

[hiroMTB]

Yeah, I'm happy to try but sometime in this year...

…

On Tue, Mar 3, 2020, 12:27 PM Michael Saup ***@***.***> wrote: @hiroMTB <https://github.com/hiroMTB> thank you. Are you going to give your fix-suggestion a try? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1?email_source=notifications&email_token=AABPGACYEHGLEONRYGZTRQ3RFTSQRA5CNFSM4KVO4RD2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOENTECTQ#issuecomment-593903950>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABPGAGX2WJOJW7FY23GIWTRFTSQRANCNFSM4KVO4RDQ> .

[johanjohan]

great, keep me posted