Detect decals after scaling happens, use glPolygonOffset instead of m…

README.md

@@ -103,9 +103,10 @@ A typical solution to this problem is to have the second player connect via a VP
 
 ## Known issues
 * There is a bug in networked multiplayer where specific types of lag spikes cause the game to lose track of timing and [play old frames at an advanced rate](https://www.youtube.com/watch?v=zxm1zzFzor0). Thankfully this is somewhat rare during normal play. 
-* [#26](https://github.com/avaraline/Avara/issues/26) Some levels have graphical "z-fighting" issues where geometry is too close to other geometry and our current graphics pipeline does not reconcile this correctly causing moire-like patterns. 
 * [#25](https://github.com/avaraline/Avara/issues/25) Avara's usage of SDL does not play well with PulseAudio on some Linux systems. If you get a segfault when launching, try telling SDL to use ALSA instead with `export SDL_AUDIODRIVER=alsa` 
 
+[See other active bugs](https://github.com/avaraline/Avara/issues?q=is%3Aissue+is%3Aopen+label%3Abug)
+
 
 ## Challenges overcome while porting
 Porting this game has been a heroic effort, mostly pulled off in the [span of four or five insanely productive weeks](https://github.com/avaraline/Avara/commits?after=1163cea5b338c17e406986b2926c1cdc626dccaa+34&author=dcwatson) by @dcwatson. 

shaders/avara_frag.glsl

@@ -9,7 +9,6 @@ uniform vec3 light2 = vec3(0, 0, 0);
 uniform vec3 light3 = vec3(0, 0, 0);
 uniform float ambient = 0;
 uniform float lights_active = 1.0;
-uniform float decal;
 
 out vec3 color;
 

src/bsp/CBSPPart.cpp

@@ -109,13 +109,7 @@ void CBSPPart::IBSPPart(short resId, char* levelsetName) {
     maxBounds.z = ToFixed(doc["bounds"]["max"][2]);
     maxBounds.w = FIX1;
 
-    float sigma = .001f;
-
-    isDecal = (
-        std::abs(maxX - minX) < sigma ||
-        std::abs(maxY - minY) < sigma ||
-        std::abs(maxZ - minZ) < sigma
-    );
+    isDecal = false;
 
     pointTable = (Vector *)NewPtr(pointCount * sizeof(Vector));
     polyTable = (PolyRecord *)NewPtr(polyCount * sizeof(PolyRecord));
@@ -159,6 +153,14 @@ void CBSPPart::IBSPPart(short resId, char* levelsetName) {
 void CBSPPart::PostRender() {}
 
 void CBSPPart::UpdateOpenGLData() {
+    float sigma = .001f;
+
+    isDecal = (
+        std::abs(maxBounds.x - minBounds.x) < sigma ||
+        std::abs(maxBounds.y - minBounds.y) < sigma ||
+        std::abs(maxBounds.z - minBounds.z) < sigma
+    );
+
     if (!AvaraGLIsRendering()) return;
     glDataSize = totalPoints * sizeof(GLData);
     glData = (GLData *)NewPtr(glDataSize);

src/util/AvaraGL.cpp

@@ -67,7 +67,7 @@ float skyboxVertices[] = {
     };
 
 GLuint gProgram;
-GLuint mvLoc, ntLoc, ambLoc, lights_activeLoc, projLoc, viewLoc, decalLoc;
+GLuint mvLoc, ntLoc, ambLoc, lights_activeLoc, projLoc, viewLoc;
 GLuint light0Loc, light1Loc, light2Loc, light3Loc;
 
 GLuint skyProgram;
@@ -170,11 +170,6 @@ void AvaraGLLightDefaults() {
     AvaraGLSetAmbient(0.4f);
 }
 
-void AvaraGLSetDecal(float active) {
-    glUseProgram(gProgram);
-    glUniform1f(decalLoc, active);
-}
-
 void SetTransforms(Matrix *modelview, Matrix *normal_transform) {
     glUniformMatrix4fv(mvLoc, 1, GL_FALSE, glm::value_ptr(ToFloatMat(modelview)));
     glm::mat3 normal_mat = glm::mat3(1.0f);
@@ -201,7 +196,6 @@ void AvaraGLInitContext() {
     ntLoc = glGetUniformLocation(gProgram, "normal_transform");
     ambLoc = glGetUniformLocation(gProgram, "ambient");
     lights_activeLoc = glGetUniformLocation(gProgram, "lights_active");
-    decalLoc = glGetUniformLocation(gProgram, "decal");
     glCheckErrors();
 
 
@@ -222,7 +216,6 @@ void AvaraGLInitContext() {
     groundColorLoc = glGetUniformLocation(skyProgram, "groundColor");
     horizonColorLoc = glGetUniformLocation(skyProgram, "horizonColor");
     skyColorLoc = glGetUniformLocation(skyProgram, "skyColor");
-
 }
 
 void AvaraGLDrawPolygons(CBSPPart* part) {
@@ -259,9 +252,11 @@ void AvaraGLDrawPolygons(CBSPPart* part) {
 
     // if we're drawing something thin
     // give it a little z-buffer push towards
-    // the camera by scaling down the z-value
-    if (part->isDecal) {
-        AvaraGLSetDecal(.9995f);
+    // the camera by scaling the z-value
+    bool decal = part->isDecal;
+    if (decal) {
+        glEnable(GL_POLYGON_OFFSET_FILL);
+        glPolygonOffset(-1.0, 1.0);
     }
 
     SetTransforms(&part->fullTransform, &part->itsTransform);
@@ -275,8 +270,8 @@ void AvaraGLDrawPolygons(CBSPPart* part) {
     glDisableVertexAttribArray(2);
 
     // reset z-buffer scale
-    if (part->isDecal) {
-        AvaraGLSetDecal(1.0);
+    if (decal) {
+        glDisable(GL_POLYGON_OFFSET_FILL);
     }
 
     // restore previous lighting state
@@ -295,6 +290,7 @@ void AvaraGLDrawPolygons(CBSPPart* part) {
 
     glBindBuffer(GL_ARRAY_BUFFER, NULL);
     glCheckErrors();
+
 }