OpenGL imgui slider ranges

Question

I have a 960x540 window I'm creating using OpenGL. Rendering one texture here and using imgui to implement a slider that let's me translate the x, y, and z positions at runtime.

int window_width = 960;
int window_height = 540;

window = glfwCreateWindow(window_width, window_height, "Object Oriented OpenGL", NULL, NULL);

First I set the slider default values.

glm::vec3 model_matrix_translation(200, 200, 0);

Later in my loop that renders the objects positions frame by frame as long as the window is open, I set the ImGui::SliderFloat3 v_min and v_max params to be the dimensions of my window. It appears all 3 sliders x,y, and z use these values, but is there a way to set a range for each individuals slider? As you can see my slider for the y axis can go beyond 540.

while (!glfwWindowShouldClose(window))
{
    // renderer and other code before this point
    {
        ImGui::SliderFloat3("Model Matrix Translation", &model_matrix_translation.x, 0.0f, 960.0f); 
    }
    ImGui::Render();
    ImGui_ImplGlfwGL3_RenderDrawData(ImGui::GetDrawData());

    glfwSwapBuffers(window); 
    glfwPollEvents();
}

score 2 · Accepted Answer · answered Oct 14 '19 at 08:44

The implementation of SliderFloat3 delegates to SliderScalarN, which is implemented as such:

bool ImGui::SliderScalarN(const char* label, ImGuiDataType data_type, void* v, int components, const void* v_min, const void* v_max, const char* format, float power)
{
    ImGuiWindow* window = GetCurrentWindow();
    if (window->SkipItems)
        return false;

    ImGuiContext& g = *GImGui;
    bool value_changed = false;
    BeginGroup();
    PushID(label);
    PushMultiItemsWidths(components, CalcItemWidth());
    size_t type_size = GDataTypeInfo[data_type].Size;
    for (int i = 0; i < components; i++)
    {
        PushID(i);
        if (i > 0)
            SameLine(0, g.Style.ItemInnerSpacing.x);
        value_changed |= SliderScalar("", data_type, v, v_min, v_max, format, power);
        PopID();
        PopItemWidth();
        v = (void*)((char*)v + type_size);
    }
    PopID();

    const char* label_end = FindRenderedTextEnd(label);
    if (label != label_end)
    {
        SameLine(0, g.Style.ItemInnerSpacing.x);
        TextEx(label, label_end);
    }

    EndGroup();
    return value_changed;
}

For your purposes, you will need to use a modified version of this function that moves v_min and v_max along with v, so in your modified function, change the last line of that for loop to:

v = (void*)((char*)v + type_size);
v_min = (void*)((char*)v_min + type_size);
v_max = (void*)((char*)v_max + type_size);

Or just specialize the whole function to take float* instead and then you can just do v++, v_min++, v_max++; instead.

Finally, you can call your modified function as follows:

float mins[] = {0.0f, 0.0f, 0.0f};
float maxs[] = {960.0f, 540.0f, 0.0f};
MyModifiedSliderFloat3("Model Matrix Translation", &model_matrix_translation.x, mins, maxs);

OpenGL imgui slider ranges

1 Answers1