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Add 'fit to scene' feature to examples/viewer #425

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4fd8c8a
Initial plan
Copilot Mar 27, 2026
04b113d
Add 'fit to scene' feature to examples/viewer
Copilot Mar 27, 2026
05afe28
Deduplicate camera reset via FitToScene
Copilot May 20, 2026
98840c2
Remove duplicate FitToScene declaration
Copilot May 20, 2026
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51 changes: 37 additions & 14 deletions examples/viewer/viewer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -157,6 +157,10 @@ float g_angleY = 0.0f; // in degree
bool g_show_wire = true;
bool g_cull_face = false;

float scene_bmin[3] = {0.0f, 0.0f, 0.0f};
float scene_bmax[3] = {0.0f, 0.0f, 0.0f};
float scene_maxExtent = 1.0f;

GLFWwindow* window;

static std::string GetBaseDir(const std::string& filepath) {
Expand Down Expand Up @@ -923,6 +927,8 @@ static void reshapeFunc(GLFWwindow* window, int w, int h) {
height = h;
}

static void FitToScene();

static void keyboardFunc(GLFWwindow* window, int key, int scancode, int action,
int mods) {
(void)window;
Expand Down Expand Up @@ -959,6 +965,11 @@ static void keyboardFunc(GLFWwindow* window, int key, int scancode, int action,
g_cull_face = !g_cull_face;
}

if (key == GLFW_KEY_F) {
// fit to scene
FitToScene();
}

// init_frame = true;
}
}
Expand Down Expand Up @@ -1088,9 +1099,15 @@ static void Draw(const std::vector<DrawObject>& drawObjects,
}
}

static void Init() {
static void Init() { FitToScene(); }

// Reset camera to fit the entire scene in view.
static void FitToScene() {
trackball(curr_quat, 0, 0, 0, 0);

g_angleX = 0.0f;
g_angleY = 0.0f;

eye[0] = 0.0f;
eye[1] = 0.0f;
eye[2] = 3.0f;
Expand Down Expand Up @@ -1126,6 +1143,7 @@ int main(int argc, char** argv) {

std::cout << "W : Toggle wireframe\n";
std::cout << "C : Toggle face culling\n";
std::cout << "F : Fit to scene\n";
//std::cout << "K, J, H, L, P, N : Move camera\n";
std::cout << "Q, Esc : quit\n";

Expand Down Expand Up @@ -1154,14 +1172,19 @@ int main(int argc, char** argv) {
return -1;
}

float maxExtent = 0.5f * (bmax[0] - bmin[0]);
if (maxExtent < 0.5f * (bmax[1] - bmin[1])) {
maxExtent = 0.5f * (bmax[1] - bmin[1]);
scene_bmin[0] = bmin[0]; scene_bmin[1] = bmin[1]; scene_bmin[2] = bmin[2];
scene_bmax[0] = bmax[0]; scene_bmax[1] = bmax[1]; scene_bmax[2] = bmax[2];
Comment on lines +1175 to +1176

Copilot AI Mar 27, 2026

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The chained assignments for scene_bmin/scene_bmax on single lines reduce readability and make diffs harder to review. Consider formatting these as one assignment per line (or using std::copy) for consistency with the surrounding style.

Suggested change
scene_bmin[0] = bmin[0]; scene_bmin[1] = bmin[1]; scene_bmin[2] = bmin[2];
scene_bmax[0] = bmax[0]; scene_bmax[1] = bmax[1]; scene_bmax[2] = bmax[2];
scene_bmin[0] = bmin[0];
scene_bmin[1] = bmin[1];
scene_bmin[2] = bmin[2];
scene_bmax[0] = bmax[0];
scene_bmax[1] = bmax[1];
scene_bmax[2] = bmax[2];

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scene_maxExtent = 0.5f * (bmax[0] - bmin[0]);
if (scene_maxExtent < 0.5f * (bmax[1] - bmin[1])) {
scene_maxExtent = 0.5f * (bmax[1] - bmin[1]);
}
if (maxExtent < 0.5f * (bmax[2] - bmin[2])) {
maxExtent = 0.5f * (bmax[2] - bmin[2]);
if (scene_maxExtent < 0.5f * (bmax[2] - bmin[2])) {
scene_maxExtent = 0.5f * (bmax[2] - bmin[2]);
}

FitToScene();

while (glfwWindowShouldClose(window) == GL_FALSE) {
glfwPollEvents();
glClearColor(0.1f, 0.2f, 0.3f, 1.0f);
Expand All @@ -1178,23 +1201,23 @@ int main(int argc, char** argv) {
up[1], up[2]);

float center[3];
center[0] = 0.5 * (bmax[0] + bmin[0]);
center[1] = 0.5 * (bmax[1] + bmin[1]);
center[2] = 0.5 * (bmax[2] + bmin[2]);
center[0] = 0.5f * (scene_bmax[0] + scene_bmin[0]);
center[1] = 0.5f * (scene_bmax[1] + scene_bmin[1]);
center[2] = 0.5f * (scene_bmax[2] + scene_bmin[2]);
float rotm[4][4];
turntable(g_angleX, g_angleY, center, rotm);

build_rotmatrix(mat, curr_quat);
glMultMatrixf(&mat[0][0]);

// Fit to -1, 1
glScalef(1.0f / maxExtent, 1.0f / maxExtent, 1.0f / maxExtent);
glScalef(1.0f / scene_maxExtent, 1.0f / scene_maxExtent,
1.0f / scene_maxExtent);
Comment on lines +1214 to +1215

Copilot AI Mar 27, 2026

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scene_maxExtent can become 0 (e.g., degenerate geometry where bmin==bmax on all axes), which would make glScalef(1.0f / scene_maxExtent, ...) divide by zero and propagate INF/NaN through the modelview matrix. Consider clamping scene_maxExtent to a small positive epsilon (or falling back to 1.0f) after computing it, and/or early-out when bounds are invalid.

Suggested change
glScalef(1.0f / scene_maxExtent, 1.0f / scene_maxExtent,
1.0f / scene_maxExtent);
float scale = 1.0f;
if (scene_maxExtent > 0.0f) {
scale = 1.0f / scene_maxExtent;
}
glScalef(scale, scale, scale);

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#if 0
// Centerize object.
glTranslatef(-0.5 * (bmax[0] + bmin[0]), -0.5 * (bmax[1] + bmin[1]),
-0.5 * (bmax[2] + bmin[2]));
#endif
glTranslatef(-0.5f * (scene_bmax[0] + scene_bmin[0]),
-0.5f * (scene_bmax[1] + scene_bmin[1]),
-0.5f * (scene_bmax[2] + scene_bmin[2]));

Draw(gDrawObjects, materials, textures);

Expand Down